User blog comment:AquilaeAltair/OnS Theories. Seventeenth Theory - The 7 seraphs of the end. Is it possible that new Seraphs can exist or are they in front of us?/@comment-36009152-20190820014849/@comment-38762161-20190903041659

Hm, I don't think Yoichi's sister will return mainly because in order to boost or activate their seraphs, they'd need drugs haha.

But yes, you're right, new characters can be introduced just like the vamp from chapter 80, that was something I didn't expect in the whole sense of Kagami's story haha.

Hm, also, this Michaela trait...I'm starting to guess that it doesn't work like the Seraph trait but in fact, it gives special conditions to those who bear the Michaela trait.

Just like LauraTepes mentioned, it's something deeper but out of those who main hold the trait, there's few who might actually detonate it to the fullest which is something we saw with Ashera