|Volume||Light Novel Volume 5|
Welcome to the World of Otomege
Time Machine is chapter 59 of the Boku wa Tomodachi ga Sukunai light novel series. It is chapter eleven of volume five.
Arriving in the club-room, Kodaka is welcomed by a blonde Rika. After pointing out Rika's new hairstyle, Rika complains as Kodaka is unable to say anything more about her hairstyle and introduces to him her own-made hair dye. Kodaka bluntly remarks on Rika's inventions being plain as she asks Kodaka on what she should invent instead. After listing a few outlandish suggestions, he ultimately comes up with a time machine.
The next day, Rika invents the time machine and uses it on Kodaka. In his consciousness, Kodaka returns ten years in the past on the day before he left the city and where he and Sora promised to converse on something important. Before Sora left, Kodaka calls out to him and reveals to her that he is leaving the city the next day and will not be able to return for the next ten years. As Kodaka repeatedly apologizes to Sora, the latter transforms into several monsters while wielding deadly weapons and using it against Kodaka in an attempt to kill him. Afterward, Kodaka is left unconscious as he returns back to the present.
After removing the time machine from his head, Rika apologizes to Kodaka for lying about her invention, revealing what she devised is actually a sleeping agent with a hypnotism feature that allows the user to dream of anything as long he/she desires or imagines it. As Kodaka apologizes to Rika for calling her inventions plain, Kodaka reveals to him that he was able to return ten years in the past. As Rika gazes towards Kodaka with suspicion, Sena asks Kodaka why Yozora appeared in his dream from ten years ago.