Korra would likely be very cautious at first. She's used to dealing with powerful opponents, but Hollow Ichigo's otherworldly nature would be something new. She might try to communicate with him, but if he showed aggression, she'd be ready to fight. Asami would probably be more strategic, trying to figure out his weaknesses. Mako and Bolin would be a bit more intimidated. Mako might use his lightning - bending as a first line of defense, while Bolin would be thinking of ways to use his earth - bending to either trap or slow down Hollow Ichigo.
Some of them might be excited. They could see new ideas and interpretations of their world that they hadn't thought of before. For instance, if there are new bending techniques in the fanfiction, the benders in the gaang might be eager to try them out in their imagination. Others might be more critical and point out inaccuracies compared to their real - life experiences in the Avatar world.
The Legend of Korra comics are definitely worth a read. They capture the essence of the franchise and bring fresh perspectives. The quality of the storytelling and the visuals make them a great addition to the series.
The 'lemon' aspect might be a bit hard to come by in a clean way as it often involves inappropriate content. But for normal Korra and Mako fanfictions, you could also try FanFiction.net. Some stories there might show their relationship developing, their adventures together, and how they support each other, which can be really interesting to read.
She could also get angry. Korra is a strong - willed character. After the shock wears off, she might lash out at Asami. She could yell and demand an explanation. She might feel that she has been wronged and wants Asami to know how much she has hurt her.