You were dating Eren for five years but you didn't even realize when you fell in love with Levi, he was older, and shorter than Eren but something about him drove you crazy.

Levi was also unable to control himself around you, he knew you were Eren's but still he tried to get close to you, he did find ways to touch you. Sometimes he'd give Eren extra missions to spend more time with you.

And that's how you ended up cheating on your boyfriend, sleeping with Levi countless times.