Sensei, Gaman Dekimasen

"It's famous that teachers never fall for you"
Kiryu, the only alpha teacher at a public high school attended by betas and omegas, is immensely popular with the students for his handsome looks and friendly personality. Kiryu is able to work at a public school thanks to his unique constitution that makes him immune to pheromones, and on the first day of school, most of the students fell in love with him when he said, "I'm not interested in kids, but I'll definitely protect you guys."
One of the students who is attracted to Kiryu is an omega, Aoki Koya, who recently had his first heat stroke at school and has been developing special feelings for Kiryu, who helped him. And since that day, Kiryu's behavior has changed...

(Source: Renta JP)

Note: Chapter count includes two extras.