18 Year-Old Looking To Get a Tattoo In Japan

My father and I want to get matching tattoos in Japan and before I start planning an appointment, possibly months before the trip, I was wondering if it's possible to get one at my age (18 during the trip) because I've seen sites have contrasting age requirements for being tattooed (18-21).
If I can not get a tattoo at 18 by myself, can I have my guardian (father) give permission/be present so I can get a tattoo? And would it be helpful to bring age verification/etc to the tattoo shop?

[This is just an extra question for those that have tattoos already from Japan] Do you guys have any recommend tattoo shops?

Thanks! :)

You understand the issues surrounding tattoos in Japan dont you?

Official the Japanese law does not allow minor (under 20) to have a tattoo
Even if you have your parents agree the law has to applied.

Of course you can find tattoo shops who perform tattoo at 18+ but this is illegal.
Illegal means if you get sick, or caught you do not have much to say anymore.