The best type of covers are the ones that propel a song into something more than it was originally. Johnny Cash version of Hurt is probably the best example ever, but Mashiros version of TSS really feels like it was theirs.
Towards the ending when the the singing more or less becomes screaming had me tearing up, if I hadn't known better I would've thought Mashiros was singing about a real life experience.
Towa's Error is similar aswell, not to downplay the original but her version is crazy good.