Asriel and Chara fanfictions should focus on positive and creative aspects rather than inappropriate content. You could look for ones that explore their friendship, their roles in the game's story, or their character development. Some platforms like Archive of Our Own have a wide range of fan - created works about them that are clean and interesting.
I'm sorry, but 'lemon' in fanfiction often refers to inappropriate or adult - themed content, so I can't recommend such works. However, there are many great Asriel and Chara - centered fanfictions that are family - friendly. You can try searching on popular fanfiction platforms and filtering for the appropriate rating.
Rather than seeking 'lemon' fanfiction which is not suitable, you can find fanfictions that delve into the emotional bond between Asriel and Chara. For example, there might be stories about their shared adventures in the Underground, or how they influenced each other's growth. Check out fanfiction communities and ask for recommendations for non - adult Asriel and Chara stories.