Tetsugaku LetraTetsugaku Letra.

Tetsugaku Letra (Japanese: 鉄楽レトラ, Hepburn: Tetsugaku Retora) is a Japanese manga series written and illustrated by Mizu Sahara. It was serialized in Shogakukan's shōnen manga magazine Monthly Shōnen Sunday from April 2011 to December 2014, with its chapters collected in six tankōbon volumes.