It looks like the main thing holding you back is just not hanging out with certain girls. If you want minimal spoilers, I'd say just spend more time with Maya, Miku, and Chika. But if you want exact triggers, I'll give ya those too.The scientific Research , events before scientific research have already been triggered, and events after scintific research that have been triggered Is a contractions , milk egg and water, and stronger i become
Scientific Research is triggered on a Friday after you do Chika's "A Castle for Everyone" event.
Parasite is triggered after Miku's "You and Me and the Night" event.
Neither of those are really required to progress the main story though. The next thing that really progresses the main story is "Recall" which is triggered on a Monday after doing Maya's "You and Me" event.