I have a crazy idea about how Buu could bring Brenda back into the game (of course, for those of us who don't want to see her dead and want to see her back in the game). Here's the idea: Brenda could be seen dead, but she had the MC's semen; what if the MC unlocks a new ability? The protagonist's DNA could fuse with the DNA of another non-human girl and acquire some of her abilities, but it would be in a specific order. A clear example would be Eliza. Eliza was the first girl the MC met upon his return, and then she turned into a vampire. By having sex with a human girl, she could acquire one or two abilities from the MC and the other non-human being, but to a lesser extent. In this case, Brenda could have acquired some of the MC's strength and durability (to a lesser extent) and Eliza's resurrection and agility. Brenda would return a little stronger (like a normal vampire), but she would not be as strong as Eliza and the MC, as she is only human, albeit with improvements. Another example would be Alice; Alice was the second girl we saw (I know it was Irene, but so far Irene is a normal human), and it would be good if Alice became a dragon girl and acquired skills. The girl (human) who has sex with the MC (and the protagonist has already acquired the DNA of Alice turned into a dragon girl) could acquire 1 or 2 skills. The MC's strength and wind manipulation and a dragon's fire breath and durability, but to a lesser extent.