Genji(when he was still human)had tattoos similar to Hanzo's.Some were clan relataed,but some were modern,like arrows and and flowers and stuff.Hanzo didn't approve and made him cover them up.Thats why Genji doesnt have his chest out like Hanzo.
When Mercy was giving Genji a robotic body,she pulled down his scarf to reval Japanese characters.She didn't know what they meant.No one knew.

"罪悪感"

Sometimes Genji will feel the back of his neck.Its not there anymore.Its hard to believe.But its not there.