>>110806787Fan-service answer: They were secretly attracted to each other, and Kim discovered her secret bi side with Lisa after Scott left for TO.
Probable answer: They remained close because making friends in a small town after a certain age is hard, they likely bonded after the Scott saga, and the rest of their high school life involved them having normal high school antics.
My reasoning for the "probable" answer is because Lisa and Kim were based on characters named Lisa and Kim in one of his earlier comics about two high school girls in small town Ontario and their wacky antics. Even if Kim were attracted to Lisa, book 4 she seemed more interested in catching up after so many years, while Lisa seemed more interested in banging Scott, in her own sort of high school nostalgia.