Shuuko is also noticeable for her cold mannerism as a lone wolf but slowly adapts to a more sincere girl through her change.
And through that, relationship are developed that can be everlasting.
If the writers would have put the revelations about Kou's past at the start of the show and, then had Futaba and Yuuri try to get with him everything would have made more sense and, Kou wouldn't have had to have a forced character reset.
For reference the most useful side character is Kou's brother whose only job is to feed Futaba information about Kou and, his back story.
But nonetheless, studio Production I.
A cleaner set-up to situations.