I want to change my surname in Japan

I am a japanese citizen and my hubby is a filipino and we've been merried for 5years now. We do it at philippines but we registered our marriage contract here in japan soon after. Since then, i still using my last name and not my hubby's last name. Also our kids are using my last name. And now, i wan't to change my last name to my huuby's name. So my question is, what paper or what should i do to change my surname. Will my japanese citizenship will be gone and me and my kids will become philippine citizen when our last name changed into filipino last name? Thankyou

Since itfs been some years since you reported your marriage to the Japanese authorities, you need to get a permission from a family court to change your family name.

This is just a link from a law firmfs website (not a personal recommendation):
https://uji.jiyugaoka-law.com/uji-henkou/pattern.html

I donft know what can be done about your childrenfs namec

Name and citizenship are two separate issues.