Senpai no Toumei na Kanshoku

The senpai that the ghostly Miou met was..!? The mysterious senpai makes her heart pound!

Mio, who has a ghostly presence, has been alone since entering high school, unable to make any friends. One day, when she goes to a classroom in the old school building where no one should be, Yanase-senpai, who attends the same school, suddenly appears. He offers to help Miou make friends, but in return he tells her to keep a promise. As she meets Yanase-senpai, Miou realizes she has feelings for him, but...

(Source: Shueisha, translated)

Note: Includes one extra chapter.