Imagine Vanitas remembers his life as a Union Member during the age of Fairytales back when he was still Ventus.
Imagine Vanitas deeply misses his old friends (especially Chirithy, his best friend).
Imagine Vanitas grieves for them every day and that’s where his sad Unversed come from.
Imagine Vanitas thinking about Chirithy every now and then and remembering how Chirithy always told Ventus not to give in to his darkness.
Imagine Vanitas hating himself because he is darkness incarnate and Chirithy would hate what he’s become.