On the way back to the mountains to get Kirishima some remedial dragon fire-breathing lessons, Bakugou agrees to let Kirishima scentmark him so the other dragons don't get any fresh ideas (if 'agrees to' means 'is completely into it').

Apparently bad things really did come in threes, Bakugou thought wryly, as the firefighter closed the distance between them. Tall, tan, and jacked as hell, he was a strong contender for the single hottest person Bakugou had ever seen in his life. He was covered in soot and sweat that contoured his ridiculous muscles, making them look even more defined, and his clinging black tank top didn’t do much to hide the rest of him, either. His strong cheekbones and jaw had smears of black on them too, and Bakugou had the absurd thought that he wanted to lick them clean. Bakugou didn’t think it was possible, but he felt himself turning even redder. He would barely have been able to talk to someone as attractive as him on a good day, and he was about to have to explain to him that he’d tried to burn down his fucking house because he was being petty on Twitter. Super.

When people start dying on the ship, Bakugou has to rush to find out what is going on. Along the way, he has to deal with the grief of losing the people he loves, and the fear that he might be next. At least, he has Kirishima by his side...