For an alternate, less insane theory about Mr. Minase.
Akiko was a Key Protagonist.
She’s had her harem, she picked Mr. Minase, she got her dicking off him. And then because it’s Key, there was tragedy, and he had to vanish. This is why she’s so utterly accepting of crazy magic shit and Yuichi disappering every night in Mai’s route, there is also a wooden sword in her attic for SOME REASON.
