noun
non-Japanese person who has adopted a Japanese lifestyle
A somewhat niche term, often used in discussions of cultural assimilation or expatriate life in Japan. It carries a slightly exotic or humorous tone.
from French tatamiser
彼はすっかりタタミゼになって、毎朝味噌汁を飲んでいる。
He has become a complete tatamisé, drinking miso soup every morning.