[Santo will take it about as seriously as he takes anything else, but he just wants to make sure that Raph knows what he's getting into. It's not every day that someone who can take a punch from him is someone that he doesn't want to actually hurt.

Raphael agreed to this though, so Santo won't be holding back... Except for making sure that he doesn't punch Raph off the roof, shoot his fists at him, or explode near him.]

Lot's of reasons. I guess it started when we had to protect this one girl from like every bad guy we ever fought. People died that day, some lost body parts... Other things. [Santo replies. He blocks the first kick, but the second one gets by and hits him. He doesn't seem bothered by the blow obviously, but it's clear that Santo doesn't have the same level of martial arts training, especially since he's telegraphing his followup punch.] Other stuff happened after that, and mutants split into two groups. One side thought we should be an army, and the other one thought we should try to be just people... I chose the one that was less likely to get my friends killed.

[It's not something Santo talks about easily, if ever. But, again, he trusts Raphael. He's strangely okay with letting his guard down with him while pretending not to actually have feelings.]