The colored page is fan colored. The scanlators themselves made it. So they might have misunderstood. Hence, the conversation saying nemo is shaved is wrong too.
The last pages reveal everything about the seme’s plan.
1. He overheared the conversation about the small d*ck.
2. Felt pressured to do something because a popular girl is about to confess to the uke.
3. Shaved his d*ck to make up an excuse to manipulate the uke.
4. Used the bully to make uke feel pity towards him (he lent the bully the game manual in exchange for telling the uke about him seeing the seme and uke walking home together).
And about the shaving thing, there are plenty of places to shave when you’re desperate.
Everyone's saying that the seme had shaved himself to be able to ingratiate himself to the uke by having a similar complex, but he only found out about the tiny dick like 2 seconds before entering the bathroom where Todo was bathing, and from what I can tell, they were all sharing a room and that was the only bathroom for that room, and the only other one was the shared bath which had everyone else in it. So I don't think he'd have had time to shave himself. And the color page showed the hair to be light brown and not black. Most people, drapes match the curtains, ya know? Not to mention, the ExiledRebels convo at the end saying they had shaved Nemo. So, just my thoughts, but I think it's likely he really did have no pubic hair.
However, I do think he was a bit manipulative. Just jacking off like that, no man will grow longer, or else there would never be a need to have penis-extension surgeries, as every man would have 12-inchers. And if he'd really did his research like he'd said, he'd know that simply massaging inverted nipples to be outside won't actually fix the issue. It'll pop 'em out for a bit, but then they'll sink back in. I do believe Yamamoto was taking advantage in that aspect, but I also really do think he was bald there.
Long rant, sorry.