Begin by showing how the friendship faded gradually. They started to have less and less time for each other because of work or new relationships. The sad part is when they finally realize it's too late to go back to how things were. They pass each other on the street, with a mere nod, when once they would have stopped and chatted for hours.
One main theme could be loss. The title itself implies that there are things lost, which might refer to various aspects like relationships, memories, or a sense of self. Another theme could be change, as losing things often leads to a transformation in the characters' lives.
I'm not sure specifically as I haven't read the novel in detail. But usually in such a story, there might be a protagonist who is directly affected by the things lost in the fire. Maybe it's a person who has to come to terms with the loss of their home or loved ones.
Definitely not porn. 'Are You Lost' is a typical comic manga that focuses on story and character development. It's intended for a general audience and has no pornographic content.
If Universe 7 lost, it could lead to a major shake-up in the story's dynamics and potentially introduce new plotlines and challenges for the remaining universes.