Hear me out! About the Red Chanpuru Tattoo confirmed being tattooed somewhere on the person/members body. So my theory revolves around Suo's eye, since I figure and other people aswell figure the tattoo wouldn't most likely physically work if it where near or over his eye. What if it was his eye itself? A prosthetic eye. So let's say somehow he lost his eye when younger or whenever and lost his eye in the process, he would most likely need a prosthetic eye or an eyepatch, which he has. With a prosthetic eye you can customize it and ir have it changed out whenever. What if they customized it or hired someone (like the person who does their tattoos) so it would have their gang symbol engraved on it, like the pupil changed out for the symbol. That would also explain why he has an eyepatch instead of the Heterochromia theory. And that in the second episode he said "And before you ask about this thing, I'm only wearing it to keep the ancient Chinese spirit sealed within my eye." As for why he still wears it with his friends and in Red Chanpuru I have three reason or theories.

1. He still believes, thinks, or knows Sakura and the rest of Furin wouldn't give up on him and then eventually would come to get him knowing all of them for so long and their personalities. So he hides it just in case that path is ever crossed and is cautious when no wearing it just in case they ever do meet.

2. He's insecure about it and the way it looks. He feels gross or wrong when he sees the insignia of his home and first gang, by both betraying Furin and that it feels wrong not having that whole feeling the being whole, phantom pain and stuff almost.

3. Rebelling. It's an act of retaliation or rebel against Red Chanpuru, though I think this is the least likely theory for me but, If it was an act of retaliation I would think it's because he doesn't truly love or care for Red Chanpuru like he does Furin, Sakura and Nirei. Since I think their's something more sinister and horrible going on in the background and behind the scenes in Red Chanpuru as implied >!in chapter 217 where their at the orphanage or dojo where Bacchus and Rakta look unimpressed with Suo's kindness while Suo only smiled. Along with after they talk to the chef and he says: "Things are just going to keep getting better" he says with a smile whole Suo, Rakta and Bacchus look unimpressed, and saddened almost. Then saying that the chef's to "Carefree" and Suo follows up on the conversation saying "There are some things they're better off not knowing." As if he and they all know that something is going to happen and are apart of it.!< Overall I think Suo covering his insignia is a way of retaliation to his organization and gang like a wedding ring. Because wedding rings are traditionally worn on the fourth finger of the or your left hand, and a ring on the wrong hand or wrong finger is a sign or symbolism of either self love, self commitment or an unofficial promise of love an commitment. Like a purity ring or gor this theory retaliation in a way. Therefore wearing an eyepatch and counseling the insignia from his own members and friends would be in a way of rebelling.

SUO TATTOO THEORY TIME!