Lovers High: Shinyuu no Kareshi to Matching Shite Shimatta

Hikaru is a fourth-year university student with no romantic prospects and having trouble finding a job. When her best friend found her first boyfriend, Hikaru became impatient and started playing with a dating app. She met Kento, a handsome working man, thru the app, and they hit it off and spent the night together. Hikaru thought she was finally going to have a happy relationship, but it turned out Kento was actually her friend's boyfriend...?

(Source: Hakusensha, translated)