Sannin de Aishiaimasho?

Determined, talented and good at pretty much anything, Machiru is the most popular girl in school. She's always striving to better herself, and won't give up on anything -- especially when it comes to love! She and Suruga have been friends since childhood, but when his attention turns to the shy, quiet Hanakago, she can't stand the competition, and suggests that all three of them date! Things are going just fine at first, with Machiru and Hanakago alternating lunch periods and between-class breaks, but the rest of their friends are not coping quite as well. Can three people really be in love? (from mangaupdates)