Hmmm.. care telling me a little spoiler?? ٩(๑❛ᴗ❛๑)۶
Spoiler
Ok so first off I am not fluent in Korean, this is just what I interpreted from the pictures. So don't take this as an official translation and wait for the uploader to upload the official translation for 100% accuracy hahaha. Sooin indeed does become a vampire, but then it looks like chihwan is going to die. So Sooin saves Chihwan by having Chihwan drink his (meaning Sooin's) blood. This makes it so that Sooin and Chihwan are now links. Here is the raws https://newtoki95.com/webtoon/1400928/%EB%B0%95%EC%A5%90%EC%99%80+%EC%8B%9D%EC%82%AC
But sticking around for the comments ٩(๑❛ᴗ❛๑)۶