Hisoka and Illumi’s “friendship” in Hunter x Hunter is one of the most fascinating and ambiguous relationships in anime — part alliance, part manipulation, and maybe even a twisted form of affection.

Here’s a quick breakdown:

• Mutual Benefit: Both are powerful, intelligent, and emotionally detached. They collaborate when it serves their interests — Illumi uses Hisoka’s unpredictability, and Hisoka enjoys the thrill of being around someone equally dangerous.
• Trust (in a twisted way): Illumi is one of the very few people Hisoka actually trusts with something serious — for instance, he hired Illumi to replace him in the Phantom Troupe. That shows a rare level of confidence.
• Dark Humor & Games: Their relationship has a playful, almost romanticized menace. They flirt with danger and each other — Hisoka even openly teases Illumi about marrying him, which Illumi neither denies nor discourages.
• Underlying Threat: There’s always tension; both would kill the other if the game demanded it. It’s less about loyalty and more about enjoyment of chaos.

In short:

Their friendship isn’t built on trust or compassion — it’s built on shared madness, mutual respect, and thrill-seeking. It’s a perfect reflection of Hunter x Hunter’s moral grayness