integration; mixing in; blending in
Refers to the state or process of becoming part of a group, environment, or substance. Often used in social contexts, but also for physical mixing or penetration.
His integration into the new workplace was quick.
This paint mixes well with water.
Noun form of the verb 溶け込む (とけこむ), from 溶ける (とける, 'to melt') + 込む (こむ, 'to go into').