谁比影子更忠诚
[shéi bĭ yĭng zi gèng zhōng chéng]
"Who can be more loyal than a shadow?" uses a metaphor comparing the most trustworthy presence (shadow) to suggest a faithful ally or lover who sticks around through thick and thin. The implication is that even shadows only follow us because they are cast by our presence but this individual would still have greater devotion.