Divine Class

Hikigaya look at their face and he sighed. 

'Like always, lurking in the background' he thought to himself. He closes his eyes for a second and his mind could not help but thought of that cheeky Trickster

They did not say anything but Hikigaya laughed

Just because they did not talk doesn't mean that their body language and face expression did not talk.

He could guess that it was Loki that told him about this matter

And if Loki is the one that told them about this matter, then what is his plans? Is he trying to destroy the plans of his brother? Hikigaya knows the hidden story of Loki.

He knows the one responsible for the Multiversal Convergence is not Loki but Death Monarch and that Speedster. 

Loki takes the blame and Hirate helps him. So, he knows that Loki would never do something that would hurt his brother… hurt Death Monarch plan.