cyb-by-lang:

“Gem” is likely the wrong word. I’ve been discussing this with someone, so here’s the answers we hashed out:

• Minato: Pyrite on the back of his neck.
• Kushina: Fire Opal where her belly button would be normally.
• Kei: Agate on the back of her right hand. Alternately, in the center of her chest where Isobu’s seal is.
• Obito: Snowflake obsidian in the middle of his sternum.
• Kakashi: Mica, underside of his tongue.
• Rin: Jade, but over her heart.

I‘ve seen maybe five episodes.