Imagine Ichigo Kurosaki falling in love with a fellow Soul Reaper from another division. They meet during a joint mission. Initially, they clash due to their different fighting styles. But as they work together more, they start to understand each other. Ichigo is intrigued by her determination and skill. She, on the other hand, is attracted to his raw power and his sense of justice. They start to have secret meetings, sharing their dreams and fears. Eventually, their relationship blossoms into love, and they support each other in their duties as Soul Reapers.
In lemon fanfiction, Ichigo Kurosaki might be depicted with a different personality. Sometimes, authors explore his more emotional and vulnerable sides that might not be as prominent in the original work. For example, he could be shown in a romantic relationship where his protective nature is emphasized in a new way.
One appeal is that it gives fans a chance to see Ichigo in new and unexpected situations. Since lemon fanfiction often involves romantic or steamy elements, it can show a different side of his character that we don't usually get to see in the main series.