少年如青柠般来过少女如紫提般离去
[shăo nián rú qīng níng bān lái guò shăo nǚ rú zĭ tí bān lí qù]
The nickname describes a fleeting moment of youth: the boy passes by fresh like a lime while the girl departs elegantly as a bunch of grapes, indicating youthful and ephemeral encounters.