4 books in series

Merman in My Tub

Merman in My Tub is a 4-book series with 4 released primary works first released in 2012 with contributions by Itokichi.

Merman in My Tub, Vol. 1 (Merman in My Tub, #1)
Merman in My Tub, Vol. 2
Merman in My Tub, Vol. 3
Merman in My Tub, Vol. 4