Otonari no Tenshi-sama ni Itsunomanika Dame Ningen ni Sareteita Ken: after the rain

This spin-off of "The Angel Next Door Spoilers Me Rotten" covers events from the past and present, adapted from the original novel’s volume 5.5, along with the special edition’s short story.
Highschooler Fujimiya Amane just started living alone but already has a strange neighbor. Right next door to him lives the most beautiful girl at school, the "Angel" known as Shiina Mahiru. Their curious relationship blossomed when Amane lends Mahiru an umbrella on a fateful rainy day. Once complete strangers, now neighbors, these teens find themselves gradually drawn to each other.
A collection of sweet, impatient moments of everyday life between a blunt boy and his cute neighbor.
(Source: Manga UP!)