It became apparent that after everything that happened in your Fifth-year with the Goblin Rebellion, Sebastian killing his uncle and you sealing away the Ancient Magic that now lay dormant under Hogwarts—the next two years should have been a breeze.
But unlike what you'd hope to believe, there is always much more drama—and despite accepting your choices, one of which you decided to not turn Sebastian in, life wasn't just going to go back to "normal."
You're Sixth-year was left to basically pick up the pieces—to fix friendships, to try and forget, but instead it just made you more aware of how much it had affected everyone and over time, everyone grew apart.
Now it's your Seventh-year—things are looking better, and although everyone seemed almost normal again, it was Ominis who needed the most support and it soon became apparent that it was going to be a lot harder, than simply trying to make him forget. It was clear that his attempt at seeming fine was no longer working—not to mention his relationship with Sebastian now a mixture of confusion and strange feelings, and so it should have made sense that Ominis was perhaps more than eager to have you at arms reach.
Everything seemed to come to a head, when you find Ominis struggling with his latest Potions assignment—his frustrations of the last two years slowly being taken out on his cauldron.