Koyomi wants for all of Japan to change, and that's not gunna happen if Junichirou sticks only to Ichou Academy.
- He just may go and do that; He's already currently gunning for the position of Headmaster of the Main Branch in the story.
- He was stated to be an active genius until he made his thesis in highschool.
- Kasa was with him when he was around 17, meaning that it's likely all their relationship developed in his senior year of school.
- It's also possible that he was making the Dokodemo Door for Kasa to explore the world without needing to push her limits.