Ore-tachi ga Shinda Natsu, Tenshi no Ita Mikkakan.

"If there were only three days left in the world, what would you do?" Kousuke was on his loathing daily routine of nothingness when a weird girl that calls herself an Angel appears and tells him those words. Soon after that he decides to go to the sea with a charming girl wearing pajamas on a small trip to escape from reality.