From Good Girls Scans:

High school 2nd year student, Seo Kentaru, is quite popular in his class for his ikemen looks. One day, he decides to skip his class and rest at the infirmary, where he comes across even more popular 3rd year senpai, Ikuta Mizukai. After their first meeting, Seo decides to avoid him since he is the type he can't handle... but Mizuki keeps on approaching him on a regular basis.

Although Seo decided to avoid Mizuki initially, his eyes can't seem but to search for Mizuki everywhere. The more they meet, the more Seo becomes drawn to his charming senpai with the unusually colored eyes and hair. And along the way, he keeps on getting jealous when he sees Mizuki flirting with other girls and kisses him out of impulse.