Chronologically speaking, one of the side stories goes before KT, Mystic Eyes Alliance (or something like that), where you meet Akira. She shows up once again in KT and acts as if she already knows Shiki. Just so you don't get a bit confused, I suggest you go through Plus+Disk first, then KT. It doesn't really matter which one you do first, but it's good to know that one of the stories in Plus+Disk goes before KT.
"I settled for that shriek. Those dull vacant eyes... oiled cabbage stench of her...! [...] You know what? I'm sorry if I'm not gonna do this the way you want me to or the way you might. But I will not make an angel out of someone who wasn't an angel...!" -Chief Tyrol, on his beloved wife.
Have you heard about the saying that goes something like "drunk people and kids tell no lies"? Well, that's just a fallacy.