Otonari no Tenshi-sama ni Itsunomanika Dame Ningen ni Sareteita Ken: Memorial Vacation

Amane happens to be the next-door neighbor to the school's most beautiful girl, Mahiru, which is known by the nickname "Angel".
As they spend time together, their relationship changes from "next-door neighbors" to "lovers".

And then came their first summer vacation.

The story of this game begins in summer, when, by sheer luck, Mahiru wins tickets to a trip to Okinawa.