I think of the Morimiya situation as like getting an arranged marriage, sometimes the people don't know each other very well or at all for those situations and have it thrust upon them, but many people fall in love and learn to care for those people they know little to nothing about. I'm not a fan of arranged marriages, but this is something that works for some.
Keisuke has actually relied on Morimiya a lot in past chapters so it's not like she is a stranger and she has been forthcoming and honest about who she is and what she wants.
