3 books in series

Seven Princes of the Thousand Years Labyrinth

Seven Princes of the Thousand Years Labyrinth is a 3-book series with 3 released primary works first released in 2015 with contributions by Aikawa Yu, Atori Haruno, 花鶏 ハルノ, and 相川 有.

Sennen Meikyu no Nana Oji Seven prince of the thousand years Labyrinth 1
Sennen Meikyu no Nana Oji Seven prince of the thousand years Labyrinth 2
千年迷宮の七王子 Seven prince of the thousand years Labyrinth 3
千年迷宮の七王子 Seven prince of the thousand years Labyrinth 4