Tamachi was Mitsu's Dad's (Aki) window cleaning partner. When Aki died, Tamachi quit the guild, because he felt that he had 'destroyed the silence out there', referring to the peace and quiet he felt while cleaning windows. Jin, Haruko and Makoto still ask him to come back, but he still refuses, thinking that he will never be able to clean windows without remembering Aki dying.
Tamachi is a quiet guy, but he becomes more talkative when the topic of eggs come up. Eggs are his favourite food and he likes them cooked any way (or even just raw).