(Title)
I Was Just an Only Child Boy, Now I Became One of a Four Quadruplet Sisters

(Author)
Toharumina
とはるみな

(Synopsis)
In the bon festival which had the hottest temperature of the year. Yuki Morishima was working in a humid room with no air conditioning for the sake of a black company. When he tried to take a break he collapsed.

But when he woke up next, he became a girl, became a baby, became a part of a quadruplet. With identical girls.

(Genre)
Comedy Fantasy Gender Bender School Life

(Link)
Ch 1-55 : http://www.mediafire.com/file/no0u6ilalisyd86/I_Was_Just_an_Only_Child_Boy%252C_Now_I_Became_One_of_a_Four_Quadruplet_Sisters_%255B1-55%255D.pdf/file