“And it's said that the weight of the soul is 21 grams. […] When I thought about this character, I instantly thought of Nicolas.”
Kojima explained the origin of Heartman: most of the characters in Death Stranding have some connection to the world of the dead, and he noted that it is said the soul weighs 21 grams. He first imagined a man who could go back and forth between the world of the living and the world of the dead every 21 minutes, searching for his family, and when he thought of that character he instantly thought of Nicolas. From there the imaginary character took shape by mixing parts of Nicolas: his intellectual and otaku side (something they share), and his command of cinema, books, music and art. Casting him was risky because Refn has fans all over the world, so Kojima taught Nicolas the character throughout the process, and what made him happiest was that Nicolas loved it. After the release Kojima felt relieved: Heartman ranked first or second in popularity among the characters (with Higgs also high), and he was personally relieved to see that.
“And I thought Hartman was the perfect role for Nicolas. He only did a scan, but it's not an easy task. […] Nicolas is an intelligent type and also an otaku, which is something we have in common, I think. […] There are lots of characters in Death Stranding, but Hartman ranks like first or second place in terms of popularity.”