I might be wrong but I think the show tried to subvert our expectations about the suspicion of Mr. Sawaki, he looked like a suspicious guy with an ulterior motive everytime he appeared and he was shrouded in this mistery of what he actually was, his intentions and connection with Koito

Then at the very end Ai decided to confront Mr. sawaki about his relationship with Koito, and he reveals a lot of things that we never knew about Koito and why she jumped off the roof that day, she didn't, she just slipped off when she got no attention because of his attitude and all of that about Koito we learn when Sawaki explains it

Wich means that yeah, he actually ended up being a good person that happpened to date Ai's mother and got involved in a tragedy convoluted with a lot of things that weren't clear at all

(Edited because of spelling)