Eventually, Eren might start to investigate the reasons behind Mikasa's betrayal. If he discovers that there are more complex factors at play, like she was forced or there was a misunderstanding, he could feel a mix of guilt for his initial reaction and relief that their relationship wasn't as broken as he thought. However, if he finds out that she truly betrayed him out of her own will, he might become even more determined to carry out his plans, whatever they are, without her.
Some fans are heartbroken. Eren is a very popular character, and his death can be a huge emotional blow. They might write comments expressing their sadness and disappointment.
Well, some characters might be amused. For example, Atsushi could be a bit shocked at first, seeing the different interpretations of Dazai in the fanfiction. He might find some of the more out - there scenarios quite strange but also interesting in a way.
One common theme is family. Since the series has strong family elements, fanfictions often explore different family dynamics within the Super Lovers universe. Another theme is love and friendship, as the relationships between the characters are central to the story.
Eren would probably be very curious. He's always been eager to learn and understand new things. Meeting kids from another time would be fascinating for him. He might ask them a lot of questions about their world and how it differs from his. Levi, on the other hand, would be more guarded. He'd be suspicious at first, but once he realizes they're not a threat, he might start to warm up and show his more protective side towards the kids.
Well, let's consider each character. Shu would probably be indifferent at first, but as things progress, he might start to worry about how it could disrupt his lazy lifestyle. Ayato would be envious and might try to cause some trouble for Subaru. Laito would make inappropriate comments and try to get a rise out of them. Reiji would be the one trying to keep everything in order and make sure they follow proper procedures. Kanato would be a bit of a wild card, perhaps being overly possessive or acting out. Yui would be relying on Subaru for support, and Subaru would be ready to fight anyone who threatened his family.