In high school Shimojou tells Kuze, "Let me take you away from this shitty boring world.” Then as adults Shimojou references that by saying “…you still feel like staying in this shitty, boring world?” and Kuze replies “I want to be your equal.” These three lines are basically the summary of the story itself, but you have to read in between the lines. Shimojou thinks living a normal life is boring, which is why he joined the Yamamoto yakuza and became “bad." And that since Kuze is a cop, he is still normal and “good." Kuze becomes Shimojou’s equal by doing a bad deed and not turning Shimojou into the authorities.

Then it skips to Shimojou saying he’ll quit the life of being bad. But why? The reader is left to piece together that the reason he’s leaving is because they have finally became equals and that after such a long chase, he’s no longer bored with Kuze around. The only reason Shimojou joined the Yamamoto yakuza in the first place was so that Kuze could find and chase after him, because it was the Yamamoto yakuza that brought Kuze’s family down. So actually, Shimojou and Kuze were after the same goal: bringing down the Yamamoto yakuza.

The whole chase was an allusion to foreplay and the sex an allusion to them finally being equal. Basically, I wish the “foreplay" was longer.