nima-nima
A sly, self-satisfied grin when you're thinking about something secretly pleasing. The kind of smile you try to hide but can't.
💡Re-reading a love message — 'She was nima-nima looking at her phone all evening.'
彼からのメッセージを読んでにまにましている。
She's grinning nima-nima reading his message.
He was ___ to himself after hearing the good news.
いい知らせを聞いて一人で○○していた。