Otoko Do-ahou! Gurren Lagann was released in Japan as a bonus feature of the Limited Edition DVD release of Gurren Lagann The Movie: Childhood's End.
Kamino Kamina introduces himself to the listener, telling them to not worry about how the setting is different than the anime. Hotta Shimon tells him to focus on the battle. Kamina introduces Shimon, and their as-yet-unknown enemy (to the first-time listener) sends them flying. Nia Teppelin launches Dai-Gurren to aid Gurren Lagann. Kamina introduces her, and Gurren Lagann is knocked around again. Utsuwa Yoko yells at Kamina to get out of the missile batteries' path, but Kamina insists that first-timers will just be confused if he doesn't introduce everyone. Yoko fires anyway, and Kamina introduces her as his scary childhood friend. Then Viral Sassoon attacks with Enkidududu, and Kamina introduces him as a fired-up agent of the Teppelin Foundation. Viral next uses the remodeled Hundred Enki Force's Hundred Enki Kick to send Gurren Lagann flying. Then Rino Ronta-sensei, preferring the name Leeron, introduces himself, before telling Kamina to aim for the red, 100-armed Enkidu; that's what Viral is piloting, and the other 99 are just imitating him. Viral berates himself for picking being so self-assertive, and Kamina tosses Lagann at the red Enkidu as an attack called the Mirage-Maker to make Lagann appear like a mirage of several Laganns flying about. The real Lagann strikes the red Enkidu, sending Viral blasting off again. Kamina and Shimon shout out the title of Otoko Do-ahou! Gurren Lagann.
A baseball match between Dai-Gurren Academy and Bachika High is upcoming, and Rossiu Dekoi, an agent of the Teppelin Foundation, is acting as the head of Bachika High's baseball club. Kamina and Shimon (calling each other An-san and Shimo-tan, respectively) are energetically practicing baseball, and Awa "Areten" Tensuke swings wildly before Kamina even pitches. Then Kamina reveals to Yoko that he has received 158 cell phone messages (and even more text messages) from his rival Kurono Kitan, who looks forward to meeting Kamina on the battlefield of baseball. Getting fired up makes Kamina hungry, so he and Shimon leave for the local ramen shop (leaving Yoko to wonder why they're using the Kansai dialect).
Upon arriving, Kamina is put off by the appearance of a bald, half-naked man eating ramen there. He's already eaten 13 bowls, endangering Kamina's record of 15 consecutive servings (which nearly killed him). He challenges the bald man to see who can eat more. In the end, Kamina and the bald man are stuffed, but Kamina has 53 helpings, while the bald man has only eaten a total of 52. Kamina's record is unbeaten. Impressed by the young Japanese man, the bald man leaves Kamina a box of "legendary double noodles" and leaves (prompting Kamina to become irritated at his "eat-and-run").
Viral and Rossiu meet, Viral vaguely congratulating Rossiu on posing as a Bachika High official. After tapping Rossiu's forehead, Viral is berated hotly by Rossiu. Viral then explains to people who only saw Childhood's End, and not the TV series, that they should not worry at how different Rossiu is from how he was in Childhood's End, since he will become a bit of nasty character in The Lights in the Sky are Stars, smacking Rossiu's forehead as he does so. Rossiu berates Viral for hitting his forehead while giving "unneeded explanations", saying that they should worry for themselves first; "that man" may have come to Japan. Viral is struck by this revelation; apparently, the chairman of the Teppelin Foundation had been missing for three days. This is why Rossiu intends to defeat the Dai-Gurren Academy the very next day - the day of the baseball game. Viral and Rossiu share a sinister laugh (and Viral hits Rossiu's forehead again, prompting Rossiu's anger again).
The next day, Areten is excited for his chance to perform at the plate. Daya-sensei will be the umpire, and looks forward to working with Rossiu-sensei. Nia hears Rossiu's inadvertent pun on the Japanese phrase for "learn manners" (マナーを学ぶ Manā wo manabu), and thinks he is being funny, but he calls it a coincidence. Nia then notices Rossiu's forehead, and says that his face is shining brightly, and Rossiu gets quite irritated. Daya-sensei cools him down, saying that Nia doesn't mean to insult him. Then Buuta, Nia's pet, begins to tap Rossiu's forehead, and Nia apologises, since Buuta "just loves shiny things". On the field, Kitan vows to kill Kamina, and Shimon expresses nervousness at his behaviour. Areten's wild swinging earns him a strike-out. Kamina is up next, and earns a ball from Daya-sensei when Kitan pitches. As it turns out, Kitan's sisters Kiyou, Kinon, and Kiyaru were kidnapped by the Ginbu Clan, at the behest of the Teppelin Foundation, to force his cooperation in this plan. Ohba Jougan and Ohba "Barinbou" Rinbou threaten to turn them into tasty hamburgers if they don't keep quiet, and Ginbu Rei tells them to not let the Kurono sisters escape.
Kitan regrets what he has to do to Kamina, but has no choice but to protect his "cute little sisters", even if he had to sell his soul to the devil. Kamina goads Kitan with words of their eternal rivalry, and Kitan tosses a blood-soaked ball in Shimon's direction. He catches it, and Daya-sensei calls this toss as a ball. Shimon shows Kamina something on the ball (other than the blood), and Kamina declares that he now understands Kitan's fighting spirit, calling himself Kitan's rival. Kitan's next toss strikes Kamina on the head, apparently knocking him out. Shimon runs up and asks Daya-sensei to take Kamina to "the hospital you keep in your car". Confused, he complies, and Yoko vows to never forgive Kitan. At this point, Rossiu reveals that the Bachika High baseball players are not students, but agents with machine guns. Nia thinks that it's another pun (one she doesn't get), but Shimon tells her that it's a trap. Rossiu reveals himself as Rossiu Dekoi, of the Teppelin Foundation's Japan Subjugation Project Team. Nia thinks that Dekoi is another pun on 'deko' (the Japanese word for 'forehead'), but Rossiu vehemently states that he hates anything funny. He calls forward Kid The Quick and Iraak Hawk-Eye to show what happens to people who run away: at first, it seems like they gunned down Areten, but it turns out they fired into the air, and Areten just freaked out. They are warned that if they fail to cooperate, they will be shot. Nia is forced to hand over the activation key to Dai-Gurren. Rossiu leads her and Rino-sensei there (Kitan says that he will stay with Kid and Iraak), and activates Dai-Gurren.
Kitan is called up by his sisters, who were freed by someone. He gives appraisal to Shimon, and promptly knocks out Kid. Yoko knocks out Iraak, and asks what's going on. Gurren, piloted by Kamina and carrying Lagann, shows up; Kamina was just pretending to be unconscious. Kitan's blood-covered ball was a plea for Kamina to save Kitan's sisters, which he'd agreed to in code words. Shimon now takes control of Lagann, and with a shout of "Shutout Combining", Gurren Lagann stands against Dai-Gurren. Rino-sensei deliberately fires Dai-Gurren's weapons without making the giant Gunmen brace itself. Kitan and Yoko rush in and take out the Teppelin Foundation agents inside. Rossiu defencively presses a gun to Nia's forehead, and Nia orders Buuta to attack. She throws a shoe a Rossiu, and Yoko throws in an attack of her own, before both of them perform a Nia-Yoko Double Kick on Rossiu. Sensing the situation turning against him, Rossiu calls out for Viral Sassoon, whistling like a dog-owner as he does so.
Viral arrives in what appears to be Enkidu, angry at being called like a dog. Rossiu leaps in to "Enkidu", and Gurren Lagann smashes off its arm. Then the arm repairs itself, and Viral says that this self-repairing Gunmen is called Enki-Do-It-Yourself. Deciding to just take it out in one shot, Kamina and Shimon use Giga Drill Break, but Enki-Do-It-Yourself spins with the Giga Drill, breaking the Giga Drill Break's effectiveness. Unfortunately, Rossiu is getting nauseous from the spinning, and Viral slows the spinning to keep Rossiu from throwing up. Kamina and Shimon increase the rotation speed of the Giga Drill Break, destroying Enki-Do-It-Yourself and sending Viral and Rossiu blasting off again. Then, a black Gurren Lagann appears on Dai-Gurren's deck.
Nia identifies it as Lazengann, and Rino-sensei is fearful. Nia identifies the pilot as her father, Lordgenome Teppelin, the chairman of the Teppelin Foundation. Kamina identifies him as the bald man who did that "eat-and-run" at the ramen shop. Lordgenome uses Lazengann's Drill Bullets to subdue Gurren Lagann, but they are ultimately ineffective. Before he can continue the battle, he is contacted by a surprising individual: Kuro Nia, Nia's younger twin sister, who asks that she herself be given the right to defeat her "foolish" older sister and give the people of Dai-Gurren Academy a taste of absolute despair. Acquiescing, Lordgenome retreats, saying that he is not running away, but will return for the next Drama CD. Kamina accepts this challenge, interested in the notion that the DVD for The Lights in the Sky are Stars will have special features.
Kamina gives a Next Episode Preview: Kuro Nia is the final assassin sent by the Teppelin Foundation. Gurren and Lagann fight. Shimon's drill is pointed at Kamina. Kamina wonders why such a ridiculous story should have such a serious conclusion, or if Nakashima Kazuki even intends to finish the story (even he doesn't know, Kamina quips). Kamina states that the Otoko Series' concluding chapter, Otoko-gumi dayo! Gurren Lagann, will be included on the Gurren Lagann The Movie: The Lights in the Sky are Stars Limited Edition DVD, and tells the listener to look forward to it.
- Kamino Kamina (神野 神名) - A roughneck in Dai-Gurren Academy, Kamina pilots Gurren, the Gunmen his father constructed to oppose the Teppelin Foundation. He is a part of Dai-Gurren Academy's baseball club, and holds the record at the local ramen shop for most bowls of ramen eaten in one sitting.
- Hotta Shimon (堀田 志門) - The Maintenance Department in Dai-Gurren Academy. He pilots Lagann, which can combine with Kamina's Gurren to become Gurren Lagann.
- Utsuwa Yoko (宇津和 庸子) - The president of Dai-Gurren Academy's Newspaper Club, Dai-Gurren Academy's Motorcycle Club, Dai-Gurren Academy's Air Rifle Club, Dai-Gurren Academy's Long-Range Bombarding Club, Dai-Gurren Academy's Karate Club, etc. She is a member (and possibly the president) of every club in Dai-Gurren Academy, and is the gunner for Dai-Gurren.
- Nia Teppelin (ニア・テッペリン) - The daughter of the chairman of the Teppelin Foundation. She opposes her father's ambitions to conquer Japan.
- Buuta (月ー豕) - Nia's pet.
- Kurono Kitan (黒野 騎丹) - A roughneck from Bachika High, and Kamina's rival. He is a part of Bachika High's baseball team, but when his sisters are kidnapped by the Ginbu Clan under the Teppelin Foundation's orders, he has no choice but to cooperate with them to ensure his sisters' safety.
- Kurono Kiyou (黒野 キヨウ) - Kitan's eldest younger sister. She and her sisters are kidnapped by the Ginbu Clan (once again under the hire of the Teppelin Foundation).
- Kurono Kinon (黒野 キノン) - Kitan's middle younger sister.
- Kurono Kiyaru (黒野 キヤル) - Kitan's youngest sister.
- Viral Sassoon (ヴィラル・サスーン) - A Teppelin Foundation agent. He places a lot of concern on his hair. He pilots the Hundred Enki Forces from a 100-armed red Enkidu, and later, the self-repairing Enki-Do-It-Yourself, in Otoko Do-ahou! Gurren Lagann.
- Rossiu Dekoi (ロシウ・デコイ) - A high-ranking Teppelin Foundation agent, and leader of its Japan Subjugation Project Team. He is often the brunt of jokes about his forehead and unfortunate surname by Viral. He plots to steal the Dai-Gurren by having Kitan dispose of Kamina in a baseball game.
- Lordgenome Teppelin (ロージェノム・テッペリン) - The chairman of the Teppelin Foundation. A big eater, he first appears pretending to be an innocent ramen customer, and seemingly barely loses to Kamina in an eating contest - only to reveal that the noodles used in his ramen were twice as thick as Kamina's. He pilots Lazengann against Gurren Lagann when Enki-Do-It-Yourself is defeated.
- Daya Kaizou (打屋 海蔵) - A sensei at Dai-Gurren Academy, originally called Dayakka.
- Rino Ronta (理野 論太) - The physics sensei at Dai-Gurren Academy, originally known as Leeron.
- Kid The Quick (キッド・ザ・クイック) - A gunman hired by Rossiu to keep Dai-Gurren Academy's students in place while Rossiu takes Dai-Gurren.
- Iraak Hawk-Eye (アイラック・ホークアイ) - Kid The Quick's partner.
- Awa Tensuke (阿波 天助) - a classmate of Kamina and Yoko's. He is nicknamed Areten (アーテン). He likes playing baseball, but isn't very good at it.
- Ginbu Rei (銀部 礼) - The current head of the yakuza group known as the Ginbu Clan.
- Ohba Jougan and Ohba "Barinbou" Rinbou (大場 丈岩 and 大場 林望) - A bumbling pair of twins who serve under Ginbu Rei. They kidnapped Kitan's sisters to force his cooperation with Rossiu's plan.
- Kuro Nia Teppelin (黒ニア・テッペリン) - Nia's younger twin sister, and one of the Teppelin Foundation's top assassins. She is much more sinister than her older twin, and obeys her father unquestioningly, even if she wants the honour of dealing with Dai-Gurren Academy (and, by extension, her "foolish" older sister) personally.
- Otoko Do-ahou! Gurren Lagann gets its name from a 1970-1971 baseball anime Otoko Do-ahou! Kōshien (男どアホウ！甲子園, meaning Such a foolish man! Kōshien), hence the baseball motifs utilised throughout this installment in the Otoko Series. (Kōshien is a district located in Nishinomiya, Hyōgo, Japan; it hosts the Kōshien Stadium, which hosts high school baseball tournaments.)
- Kuro Nia (Japanese for 'black Nia') is the Japanese fandom's nickname for Anti-Spiral Nia.