We mostly speak English at home – even with her father-in-law, we mostly speak English. I have made a few English-speaking mom friends and we switch back and forth with them, and she uses only Japanese at daycare. When she started she had spent three years home alone with me and was starting basically from zero. It took about a year but she speaks pretty well now, although not as fluently as her classmates (yet). She will switch to Japanese when playing with her dad sometimes, but sort of theatrically. Like it’s part of the roleplay still and not really natural to her yet.