レジ袋はいらないよ。マイバッグ持ってるから。 — I don't need a plastic bag. I have my own bag. (Supermarket · Adv, Casual — to friend, JLPT N5)

Gesture & etiquette

Give a friendly nod or a thumbs-up while holding your reusable bag.

Do not imply that refusal of bags is a sign of stinginess or poor service; it is a common eco-friendly practice in Japan.