#0306

One option is that the two meet and fall in love normally, only for Fuuta's online snooping to lead him to some of the yakuza's crimes. In an attempt to call out these "ordinary citizens" who seem dangerously close to his lover, he ends up in the clutches of deadly gang members. Mahiru shows up, revealing her true identity, and uses her sway to free him.

Alternatively, Fuuta's dad is high enough in society and traditional enough that he's determined to ensure his son marries well. Fuuta brings up Mahiru in conversation, mentioning his feelings for her (in his tsundere way). While he was actually lamenting that she's trapped in the controlling household, his father only processes that Fuuta has fallen for a wealthy heir. He speaks to the Shiinas and arranges for the pair to be married.

Another fun choice (and inspiration behind the second sketch) is that Mahiru is open about her identity, and Fuuta tries to expose her crimes on his account. She has plenty of protections, so she hardly feels his digital attack. Instead of fear/anger, she falls head over heels over the cute little self-appointed hero she met online. She wants to dote on him, her family wants his callouts silenced, so it's decided she'll keep him as her new forced fiancé <3