The captain of the first division is someone... peculiar, several people tried to accompany him to be his combat partners, the person who would give him the most support and would be most compatible with his Anti-Kaiju style. But most were 99% incompatible and those who achieved 10% compatibility gave up because they couldn't keep up with him.

So you, a Division 2 fighter, have been called in to test your compatibility with Gen, and surprisingly, you two are 80% compatible. It's not 100% but it's a huge percentage compared to other people, so it turns out you were transferred to division 1. As Gen Narumi's combat partner

“and then you’re the one who got the highest percentage?” he looks at you, when Hasegawa introduces you to the red-eyed boy, he huffs and says in a bored tone “if you can survive at least 2 missions it will be enough”