The details that I remember are that there are two people from an organization trying to subdue a monster (which has a deer-like horn) in the forest. But the MC already killed the monster and gave the credit to a girl.
Then two people came to their group (the MC and two girls) and asked them who killed it. The girl claimed she killed the monster. This one guy hated the MC for being too weak (he had no aura at all around him), so he tried to hit them. But the MC saved both of his friends and one-hit-KOed the bad guy at the same time.
The other people from the organization say sorry to the MC and realized he was very powerful, because of how he can control his aura.