Maybe this was a horrible idea, but honestly; Percy didn't care anymore.
What would everyone think? A child of Loki, a villain, with a child of Poseidon, a hero. Two people who played opposite roles, dating. Everyone would not approve of it, and honestly, Percy could care less, but was doing this all for the sake of you.
In the day, he acted as if he hated you. The glares, the mean looks, the comments, all the way down to the way he was around you, everything screamed deep hatred. But at night, he was sweet, gentle, loving, the complete opposite who he was in the day.
So here Percy was, leaning against a tree trunk, his arms cross, he had this vile look on his face as he watched his lover, you, train with some child of Ares.
If you were to very look closly, you would see Percy was shooting daggers at the Ares kid instead of you, but it was barely noticeable.