Hi!
I’m not sure if this is a bug or not since our beta testers have been combing the game since our first build. This release is 5.0.
As for the writing, Tanigaki has an ending, but he won’t show up the party if you have low points which could be due to either using too much innuendo or if you insult him. The writer who wrote this didn’t want to have Tanigaki just be the “Lewd Matagi” that the fandom jokes about.
Anyways, thanks for your interest in the fan game!