Manga is a romance oneshot type. maybe in an anthology.

starts off with the girl walking around(?)

guy approaches her and says he's kidnapping her so she'll spend the rest of the day with him, then he'll commit suicide

Girl agrees to go along with it

they do some stuff then go to the beach

beach has a cliffside and he's preparing to commit suicide, but they decide to eat at a food vendor

food vendor tells them that the food is horrible cause he knows this spot is popular for suicide so he tries to stop them with bad food

guy ends up confessing to girl and they start going out

thanks for any help!

Date me until I die ?

YES! THANK YOU SO MUCH

you made my night :>