This is a failing of comprehension so many players of these games fail at... Just saw in another thread someone complaining about an LI going down on MC 5 min after meeting him... The LIs don't act that way with other men, in 99% of harem games, it's that MC is so powerful magical whatever, that women act out of their character, release their inner desires very quickly when meeting MC McMagidick.
Too many people try to map "realistic" behavior on the female LIs while just rolling with the ridiculousness that is the MC in every harem game.
Personally, i prefer things to be grounded over "realistic", and everything with Miss Takamura is fairly grounded, and in its way realistic.
But yea, I do agree with you, people in general, chasing after things being realistic can't see the wood through the trees.
It's all about what helps tell a good story and is grounded.
Sarah getting freaked out about her stalker and wanting MC to protect her on her way to and from her home, really realistic and grounded.
Miss Takamura getting involved with MC the way she is, certainly grounded, and realistic after a fashion. People don't always make the wisest of decisions. In this case it's fine because we all know it's going to have a happy ending (assuming I'm right about her ending somewhere between Lucy and Victoria and being a full girlfriend/wife)