It's part of a series. This is the 5th one, did you read it? The series is called Tanoshii Jogoku wo Irodoru Nara.
1st - http://www.mangago.zone/read-manga/haikyu_dj_tanoshii_jogoku_wo_irodoru_nara/
2nd - http://www.mangago.zone/read-manga/haikyu_dj_tanoshii_jigoku_wo_irodoru_nara/
3rd - http://www.mangago.zone/read-manga/haikyu_hikari_no_ko_doujinshi/
4th -
http://www.mangago.zone/read-manga/haikyuu_hikari_no_ko_2/
5th is this one you've read - http://www.mangago.zone/read-manga/haikyuu_hikari_no_ko_3/
Read them all in consecutive order and you will understand it's a lovely piece of Gusari (◍•ᴗ•◍)✧*。
ohhh...thanx!
no problem! (⌒▽⌒)
I didnt get it