This is one of those stories that, despite I put it in my "Favourite Re-readings" list I cannot read again. I am afraid to taint the wonderful feeling I was left with, since the very first time.
Omegaverse: two friends who are on the opposite sides on so many levels, though deadly attracked by each other.
Once the physical line was crossed, their encounters were frequent and their differences arose even more. The Alpha wanted to mark the omega who insistently claimed to be free. Of course, other people had plans for the main leads to fall apart.
Will such plan work?

A side note: it is not merely based on eros. Up to the end, there is a great lesson to be learned.

Before starting, I have to warn you that I did not read all the related series (only a few and one is still on going and I dropped another one). So, I apologise beforehand.
I was thoroughly fascinated by this Fan Service series because it sounds like a yaoi version of Cinderella, Omegaverse-style. An omega boy (Eren) has felt a connection with the leader and vocalist (Levi) of a band who does not show any part of his face, save the mouth. So, basically, the only thing that is known is that he has a particular voice and a certain bodyshape. Notwithstanding, Erin feels that Levi is his destined mate. And he feels safe because being an omega born with a particular condition: an hormonal imbalance attracted all the Alphas since he was very young and those Alphas repeatedly tried to force him,, Eren is extra sure that both of them will never meet each other and ergo Eren will never bear a child.
Fate plots against his wishes and Erin is chosen for a special secret meeting for Fan Service during which Levi (stage name L) is bound to satisfy any request of the chosen fan.. Eren's request was that L would be chained and blindfolded (actually even his nose should have been covered). Once they both meet, Eren feels erotic attraction to the point he assaults L who reveals to be Levi. Out of embarassment, once Eren's identity is discovered, Levi reaches out to his fan and reveals that they are fated mate. Therefore, Levi picks up from they left, the previous nights.
Days after days, months and after months, Levi does his best to let Eren become aware of their true relationship, despite they are an idol and his fan. But not everything goes as planned.
Is the Cinderella story just about a fan making his dream come true? That's just the initial spark. There is more to it.