Natanajuseyo!

One day, an ordinary college student, Kim Ji-Yong, begins to see Jung Jung-Hye in his dreams.After falling in love with her at first sight, Kim tries to find her, but it turns out she was... She committed suicide two years ago!
A bittersweet romance in which Kim Ji-Yong struggles to save her life. Show up, right in front of me!

(Source: Naver, translated)

Note: Chapter count includes 19 extras.