Is it polite for kid to call their parents their name in Japan? I've been bothered with Ak...

good point. now that you mentioned it this isn't the first time a character was calling their parents by their name or in any way expect your typical "mom" "dad".
i dont know about this if it's ok there but i know there are disrespectful names you can call them.
like "ofukurou" and "oyaji", those mean "mom" and "dad" but in a disrespectful way.

I thought that was pretty weird too.

I think it depends on the parents. Sometimes parents just want to be close to their children and let them call their name. But for traditional or old fashioned family they still call their parents otoo-san and okaa-san, some even use -sama for it to be more polite

This is just my personal opinion tho ヾ(❀╹◡╹)ﾉ~

It depends completely on the kid and the parents actually. While I lived in Japan I was often invited by a Japanese family to have dinner together. One of their kids called his parents as mom and dad, while the oldest son called his dad by name and mother simply as mom. Since Japanese people is used to call others by last names (but can't within family since they all have last names, they use given names) it's not uncommon. Akira is probably embarrassed to call him dad and Hisamitsu never told him to, that's my guess.

I think it's because he couldn't call both of them dad and maybe felt bad if he excluded toki

I guess this is one way in which US English is more formal than Japanese then... I'm in my 30s, but if I ever called my mother by her first name, she would smack me upside my head.

LOL SAME HAHAHAHHA

I was probably around 17 b4 i called my mom and dad mom and dad. Always called by their first name or verison of it. All my friends thought it was odd and said things like if i called my mom or dad by their given names they would knock me into next year. As mom now my kids call me mommy but have been taught our full names and if they choose to call us by our given names its no issue. I am from the U.S.