Yuuri-chan no Chuuken-kun

On the morning of his high school entrance ceremony, Masato Kisaragi has finally reunited with his childhood friend and crush, Yuuri Asakura, who just got back from abroad. Now that they're going to the same high school, Masato is completely at the mercy of Yuuri, yet his feelings for her only grow stronger. There is only one problem: Yuuri has an arranged fiancé, and he is Masato's brother...?!

(Source: Kadokawa, translated)