Matt could see it. Enemy after enemy, he watched as the familiar merman fought with every ounce of his might. They were all strong, too strong, but Shiro was stronger. But even that had limits. He shouldn't have expected the merman to fight like a powerful, unbeatable king, but apparently all of the quivering merfolk behind him considered him to be just that. Matt was sick of it; he could only imagine the kind of responsibility he was willing to take to protect himself and everyone, but nobody was around to help. He had to take up that burden all by himself, and Matt couldn't bear to just watch in silence.
He was slowing down, and his gills were straining to support his breathing. He was going to soon collapse and it'd be a signified loss, and the merman didn't want to think about the consequences of Shiro losing. So, with the jeers and cries of the crowd turning into forced white noise, the younger merman placed himself in a focused mindset and tried to make a decision. Shiro either gets disqualified - if that even was a thing as Zarkon sometimes sadistically joked about it - or Matt takes the situation into his own hands. The other merman did this for him before; spared him the pain and fear and burdened himself with it. The golden-eyed merman always wished he could be this brave.
But he didn't need to wish anymore. Now he could act.
He swam forward, immediately hearing the gasp of a concerned mermaid who no doubt would try to convince him against moving into the arena, but he did. It was by his own decision, and Zarkon wouldn't care as long as someone fought and got hurt. He knew he wouldn't be able to just hide behind a dodge or by protecting his face from fists, claws and teeth. He had to get his hands dirty, and he also needed to focus. Be careful. Try to limit his injuries even with such strong opponents, and instead inflict pain. He wasn't ready, wasn't powerful, but he knew he had to try. Walk out of it alive.
"Hey!" His voice uncharacteristically boomed through the arena amidst his adrenaline, the jeers suddenly quieting in confusion which turned into anticipation. They seemed to remember him from last time, scowling at him and mocking him for his immense fear. He looked at all of them before he approached the arena, filled with dread, and stood between Shiro and his opponent, who looked scaly and deformed to no end, but still had something akin to human expressions on his face. "Can you hear them? Mock me and belittle me for simply fearing for my life? I'm not having that anymore! Enough of all of you. I'm going to prove you wrong!" He yelled, turning firmly to face Shiro.
But his thoughts said something else.
He sent him the message before he harshly slammed him in the chest with his tail, dropping him out of the arena. He hoped he'd be taken away with the state he was in, far away. Then he turned to the opponent in question, straightening up.
"This is my fight, so you fight me. Let's do this."