Watashi no Machi no Chiba-kun wa.

Onodera Machi, a 27-year-old high school teacher who teaches at her former alma mater, is engaged in calculating love, judging partners by their occupations, annual incomes, and other specs with an eye on marriage. One day, a transfer student, Chiba Yuto, arrives in her class. The handsome high school student is the younger brother of Machi's first love in high school, Chiba Yuichi, and is the spitting image of him in high school! Machi can't take her eyes off Yuto as she sees her first love in a student 10 years younger than her. Meanwhile, she happens to meet her first love, Yuichi, at a drinking party...Yuto, the younger brother, is so sexy that she can't take her eyes off him, you wouldn't believe he's a high school student, and Yuichi, his older brother, is still as good-looking and handsome as he was in high school. A thrilling triangle love story that sways between "instinctive love" and "promised love"!(Source: DramaWiki)~~ Adapted from the manga series "Watashi no Machi no Chiba-kun wa." (私の町の千葉くんは。) by Okamoto Tokasa (おかもととかさ).