Its the Edo period and this takes place on the island Shinsenkyo.

Gabimaru walked back from the bath with Sagiri -Gabimaru's guard- and Mei -a little girl that couldn't speak and Hoko, a tree monster took care of her-.The three of them were just walking peacefully before they heard someone shouting something. They made out for them to be shouting "Mei". Mei left Gabimaru and Sagiri and started running towards the shouting. Gabimaru and Sagiri quickly ran after her. When they caught up they saw Mei with another person.