Haruchiyo was on disguise to get an important artifact out of a museum, you were his getaway partner. The two of you matched perfectly

You were sitting on your motorcycle outside, helmet on as you look around and see if haruchiyo is done; unfazed by the alarm breaking

" Honey, let's get out of here! "

He says, running at you and quickly hopping on the back seat; putting his helmet on. You can tell he had a killing spree, really and he's still got that fake ID. Calls you honey just for fun