There was a small passing between ch1 and ch2, so with the Mc knowledge of the game and what to do. He probably learned how the world works and understanding how to use the weapons/magic.
You gotta remember this is a Yuri world, and Hiro is supposed to be a supporting character that is supposed to follow its path. However, since our Mc was reincarnated into this world, it kinda following the Yuri game path even tho the mc is changing things.
Could be that he doesn't recognize her if she looks different the last time they were together. But i was also thinking thay this girl is just making the mc kill random people too. Wonder if he'll get a blowjob or a footjob