Yunagi Marbled (2017)

Blurb:
One evening in a seaside town, high school student Ena was walking her dog when she notices a girl by the seashore. Looking towards the sea, the girl had a melancholy expression which worried Ena. The following day at school, Ena can’t help but remember that encounter and wish she had done something, anything, to help a girl who clearly looked troubled. While she was in a state of regret, the rest of her classmates were talking about an incoming transfer student. As buzz of such news filled the room, in comes the teacher with the new student. To Ena’s shock, it was the girl she saw at the beach! She introduces herself to the class as Mishio Nanjou. From that point on, Ena was committed to stay by Mishio’s side. But after Mishio reveals the reason for her transfer, will Ena still feel the same way? How will she feel after Mishio kisses her unexpectedly?

Source: www.anisearch.com/manga/41054