Captain Spaceboy is one of the first bosses encountered in OMORI.
In 2014, the first demo of the game was shown at Anime Expo 2014 with an old version of the Captain Spaceboy fight. This version of the game did not have the signature hand-drawn art style, which was not seen until one of the Kickstarter updates showed him off in the new style.
Captain Spaceboy is first seen in the game after Omori and his friends first travel up the ladder to get to Otherworld. He is referred to as Space Boyfriend by his crew because he was originally in a relationship with Sweetheart. The group learns that he is lovesick and can't cheer him up because his Special Mixtape was thrown out. The group decides to go into the Junkyard to search for the missing mix-tape so that he can return to his old self. The mixtape is found by Rosa, a Sweetheart super-fan in search for any of Sweetheart's merchandise. Once she makes it clear she refuses to give up the tape, Omori and his friends have to chase her down to take it from her. The chase is halted when Rosa crosses a "DO NOT CROSS" tape. Once the group crosses it, a boss battle is initiated against the Download Window. Once the boss defeated, the group manages to take the mix-tape away, only to learn from Rosa that Space Boyfriend and Sweetheart had broken up. The group refuses to believe her. After properly meeting Pluto, the group flies back to the town area of Otherworld to give the mix-tape to Captain Spaceboy. The group, with the exception of Kel, learns that what Rosa had said was true. Kel plays the mix-tape and subsequently angers Captain Spaceboy. Before the fight, Aubrey decides to call him Space Ex-Boyfriend (the game renames him as such). After the boss battle, Space Ex-Boyfriend reverts back to him calm and collected self; renaming himself back to Captain Spaceboy.
Regardless of the route, Captain Spaceboy will appear after the Sweetheart boss fight to propose to her. After the two of them get married, they both fly off together. Sweetheart will subsequently divorce Captain Spaceboy; turning him from Space Husband to Space Ex-Husband. Where the routes differ is in what happens after he turns into Space Ex-Husband. If following the true route, he can be found on the Underwater Highway singing karaoke in the submarine restaurant. If following the Hikikomori Route, it will be possible to fight Space Ex-Husband at the top of Snowglobe Mountain.
Kel angers Captain Spaceboy by playing the Special Mixtape and Aubrey angers him further by calling him Space Ex-Boyfriend. Captain Spaceboy gets angrier as the fight goes on. After receiving some damage, Captain Spaceboy will become angry and cannot turn happy or sad anymore. After more damage, he becomes enraged, and subsequently becomes furious. After his defeat, he calms down, and as consolation for his not finding Basil he gives Aubrey a Sno-cone Ticket and a Train Pass.