The hashiras are at tengens house, because tengen hosted a party, and rengoku brings his younger brother, Senjuro.

Muichiro: leaning on a wall, crossing his arms, sleeping?

Rengoku: sees that Senjuro is just cleaning like usual but says to him that he can take a break for a while and make some friends! he smiles

Senjuro: nods, looks around, and sees muichiro, and starts walking up to him "u-uh...h-hello!" waves a little "i-i am S-Senjuro, w-who are you?"