Responses
No, the teacher does not have feelings for Tsurugi. She's just concerned about her sister's relationship with a very popular, good-looking boy friend. She and sister have very sad experiences with their own fathers ( they're half- sisters only ) . She doesn't want Koiko to experience the same thing.

I never understand why romance between teachers & students are glorified in Japan.... how is it normal? I mean I get the crush from student to teacher, but vice versa?! Σ(っ°Д °;)っ I really hope the sister find her own match, just to make this manga a little less disturbing