Bet he's just out for the day as he gets his mom situated in the hospital, meanwhile sensei gets the wrong idea and thinks he's dropping out which leads to some hospital shenanigans that leads to her feelings being exposed and they start dating.
That "I have to stay home everyday to care of my sick mother" message is now strangely fitting to the chapter's contents, and I feel awful by just saying that out loud
Wait, let's just back up for a second and appreciate how a hairpin fell down the back of Sensei's collar, slid all the way down, and somehow clipped itself to the crotch of her underpants.