Cain costs 1128 diamonds, far above Dmitry at 751 and Greg at 682. He also has the most free steps in Requiem, 7 of 26. The cost is spread across all three seasons, 335, 408 and 385, with three choices of 100 or more.

Where the big money goes

Season 3, Episode 7, The Interlude: "Please!" — 146.
Season 2, Episode 10: "Something more." — 143, next to a free pick of Cain.
Season 2, Episode 3, I Know Who You Are: "Go into the shower." — 100.
Season 1, Episode 9: "Open mouth." for 76 and "Touched my forehead with his hand." for 44.
Season 1, Episode 7: "No, I won't. Leave me alone." — 74.

The route starts in Season 1, Episode 1 with "Look at him." for 45. Season 1, Episode 5 has two choices at 48.

How I'd play it

I'd put the 146, the 143 and the 100 on the Diamond Rush list right away: 389 diamonds you don't have to buy. Then keep Cain on his own save slot and pay the rest as it comes. Season 3, Episode 11 has "Explain how I feel." for 70, and the same choice is on Dmitry's, Greg's and Yan's routes, so it doesn't decide much between them. Compare with Dmitry or Abel at 68.

Other love interests

Dmitry751 Greg682 Yan577 Boris146 Abel68

Questions and answers

How many diamonds does Cain's route cost?

1128 diamonds: 335 in Season 1, 408 in Season 2 and 385 in Season 3.

What are the most expensive choices for Cain?

"Please!" for 146 in Season 3, Episode 7, "Something more." for 143 in Season 2, Episode 10 and "Go into the shower." for 100 in Season 2, Episode 3.

Which of Cain's choices are free?

Seven, including "Grab Cain's hand." in Season 1, Episode 2, "Wanted him to never let me go." in Season 2, Episode 5 and "Sorry for Cain." in Season 3, Episode 5.