Kouhai Tanetsuke Onsen: Nishimura Yuki-chan ni Marking

By the time the MC fell for his underclassman, Yuki Nishimura, she had already gotten herself a boyfriend. Trying to forget about her, he tries to date other women, but it just never seems to work out. Tired from everything, the MC decides to go on a hot springs trip but Yuki suggests to tag along...
(Source: Fakku!)
Note: A live-action AV adaptation (CAWD-030) was released on November 25th, 2019.