Download link for mod is here: https://pastebin.com/rbxnawVP

To install:
Find your game directory (usually in Program Files (x86)\Steam\steamapps\common\Yakuza Kiwami)
Then navigate to media>data>chara>w64
If you want a quick and dirty installation you can drag the w64 folder from the download onto
the one in the game directory and click yes when it asks if you want to replace files.
I do NOT recommend doing this; I recommend you back up each file you're going to replace to
avoid having to redownload the game when you want to revert changes.

To make your own:
I consulted this guide for unpacking and repacking Yakuza 0 and Kiwami's archive files:
https://www.yekbot.com/yakuza-0-modding-guide/
To edit textures you will need to have Intel Texture Tools Plugin for Photoshop to open and
edit .dds files. I think there are alternative options for GIMP but I use Photoshop.
Beyond those basics, I recommend not loading Transparency as an Alpha Channel when prompted.
This will let you edit the tattoo by itself, and not the surrounding skin texture. I recommend
dropping the brightness of any image you use by about 25% at least, or as much as you can
get away with, or else it will "glow" when viewed in game.

Thanks for downloading and have fun.