Masozi is, presumably, spending the afternoon safely ensconced in his room and studying Mandarin. The first hint of something wrong is when he fails to appear at the Shanghai table for dinner, even well after all the other freshman have made it over.
"I'd like that. If you're done your homework." He looks sort of blankly at his now-empty water jug. "...Can you get me more water first?"
The last time Masozi was sick, he had to stay up all night anyway, keeping mals off his mother and sister, occasionally casting his two-hour ward over both of them and then trying to rest for a little while, with the only upside being that concentrating while feeling awful was helpful for generating mana. This is so much better! It's nice enough that he almost doesn't mind being sick, when it means that he gets snuggles and singing for an entire evening even though this is not, strictly, necessary for Lan Xichen to keep him safe from mals or make sure he's drinking water.
He thinks Lan Xichen is very good, and drowsily tells him so.