First multi-character LORA, for identical sextuplets no less. It's recommended to use negative prompts of features from other sextuplets that are not in your prompt if you don't want to generate them. Will probably update in the future since it's not perfect but as is I'd say it's decent. Inpainting + img2img recommended as the first image will likely be far from perfect.

Recommended tags:

osomatsu-san

(color) hair highlights [red/blue/etc.]

osom

karam, kara_eyes

chorom

ichim, messy hair

jyushim, open mouth, heart in mouth

todom, cat smile