I imagined the event that leads Joel and Dylan to confirm their love for each other:
Mark informs Dylan that the food reserved for the faculty is much better and tastier than the food served in the cafeteria. The latter confides the information to Joel and the two, who had noticed that their friends were getting bored of the usual things served, decide to do something crazy together: sneak into the university kitchen after lessons and steal some food, even leaving a fish in the fridge with a note that says: "Your empire of terror will end soon, you ugly bastards." That night, before continuing their explorations in the castle, Joel, Dylan and the others are seen in the camping area, where they enjoy a dinner with food stolen from the kitchen. Joel realized he had eaten too much and, as soon as he felt the need, he went away to a corner to vomit, being joined by Dylan.
Dylan: "Apparently even the princess has dark sides to her..."
Joel: "Yes, it's true. I ate like shit. But I have to admit that the first time I misbehaved it was so much fun that I didn't want to stop!"
Dylan: "The life of a mercenary is made up of ups and downs, you have to be ready for anything and enjoy the joys of life. You taught me this last thing, I thank you."
Joel: "Yes, I admit that I would like to spend more time with you..."
Dylan: “Well, you could give me a nice kiss to confirm you as my business partner.”
Joel: “I told you, I don't know if I'm your type.”
Dylan: “Well, enjoy apartment life with a bed from a sewer.”
Joel: “I know, enjoy the work of violence and blood.”
Dylan: "Definitely."
Joel was overcome by emotion, then put his hands on Dylan's face and kissed him lovingly. The latter was surprised, but then began to enjoy it.
Dylan: "...Wow, you were serious."
Joel: “It's not like I'm very good at hiding the truth.”
Dylan: “Maybe we could do better in that dump of yours.”
Joel: "Sure. But first, let's go back to the others. We have a job to do."