Madow finds himself in a desert, he can gather by the fact that it's night that this must be in a different part of the world since it is still early at the USJ. The polaris is not visible so must be the other hemisphere too.
It's extremely dry, and it will only get worse as the sun goes up. It's currently cold, but Madow could deal with that easily. Some water also got teleported with him, but it wouldn't last too long in this environment, so he should take as much advantage of the night as he could.
He can't see the sea, but he can feel it faintly from afar. So he just begins to run, running for as long as his body would allow, he wasn't specifically built for this, but his body was well trained, and most quirk would grant higher physical capabilities compared to normal people.
During the nights he ran while keeping the water he had, while during the day he would use his quirk to dig into the ground, using water to hold up the chamber.
It was still quite hot and dry, but he could avoid direct sunlight while resting. Being able to keep this up while sleeping due to unihemispheric sleep, like a dolphin.
A few days later he finally reaches the coast, his water having run out, his last meal having been that beast days ago. He doesn't wait for a second to jump in the water. He lies on the water, taking a bit of time to rest.
After that he gets some water with his quirk, separating the salt so he can drink, and catches some fish. A town can be seen in the distance, doesn't take too long to get there by water.
After getting there he tries talking to the people but the language barrier makes communication difficult, but he manages to get a place to sleep by helping the fishermen with his quirk, and finds out where he is, the town of Caldera, Chile.
He spends some time with the fisherman and his family, he can't understand much of what they're saying, but the atmosphere was quite nice. He said his goodbyes in the morning before setting off to sea, going home.
After being in the water for quite a while his body begins to relax, changing to better accommodate his constant quirk usage and facilitate highspeed travel. Occasionally stopping for rest.
After a couple of weeks, he's finally able to get back home, stopping by his lighthouse to change into his school uniform and walking to school. He takes the suit with him, battered and with a gash on the back, thankfully the cut was shallow, so it won't leave a mark on him.
On the way to school, he walks by a store, seeing the news on a TV by the window. One TV was talking about some giant sea beast that was seen in some parts of the Atlantic, looking like some mash-up of various sea creatures and the size of a ship.
On another TV they were talking about the USJ incident, a student had lost one of his arms, Madow recognized him as Nero, and another had gone completely missing, Madow recognized him as Madow.
He continued to walk to school, now a bit embarrassed by appearing on TV not once, but twice.
Arriving at school he just goes to class, going to his seat as if nothing had happened. He did it so naturally that the class had to take a couple of seconds to realize that he was back, and then promptly reacted in shock that he was fine.
"Dude! Where the hell were you!? We thought you died!" Exclaims Delsin.
"Uh, Chile." Reponds Madow.
"The fuck you mean Chile?!" Alex joins the conversation.
"The cloak guy sent me to a desert, so I just came back. Suprised he didn't send me to space or something, everyone with a teleportation quirk should have space as an option." He says, adding a sarcastic tone while looking at Alex for the end.
"I can only go to places I've been before." Alex says while the rest of the class praises Madow for getting back.
"So go to space, you'd be amazed at how often a portal to space would be handy." Then he thanked the class for their compliments, saying it was no big deal.
All Might arrives flying through the open door grabbing Madow by the shoulders and lifting him up. "Young Madow! What power! What courage! What.. Everything! You've done things even pro-heroes wouldn't dream of. It's clear you will be an amazing hero someday."
"Thank you, Mr. All Might, I hope to be even better in the future. But a quick question, will these days count as excused absences?" He says while being put down.
"Ah, yes! These won't go to your record, but you did miss some classes, so do your best to catch up" He coughs on his hand. "Well, that's all. I've been busy with the attack and you going missing, I should inform the press today." He says while flying away.
Madow walks to the front of the class, "If you would permit me, I'd like to say some word about what has happened."
"I'm very happy that you all are safe and sound, it was a great scare for all, but I hope we can use this as motivation to get even stronger and save as many people as we can."
"I'd also like to thank Bifrost, Karma, and Lucifer for their direct assistance in the fight against villains"
"And lastly, I'd like to say that everything that went wrong is Luxanna's fault, for being useless. Any questions?" Madow says with a serious expression and a fluidity to his words that if you were paying less attention the insult could have easily been missed.
She storms out off the class, saying she's going to the restroom, whilst hurling a bunch of insults at Madow. The class is laughing.
Eraser King has been banging his head against his desk for a while. "Ok, ok...but you." He yawns. "Are still my student, Mr.Hero. So sit down before I nullify your quirk and throw you in a desert."
"That's extremely insensitive to the terrible experience I just had, Mr.Aizawa." He says with a sullen face, but before Eraser King can say anything Madow snorts and walks to his seat, leaving the teacher annoyed.