A commonly-used term in romantic anime, an osananajimi is a friend from infancy, a childhood friend or old playmate with whom one shares the special and intimate understanding that (according to such stories) can only come from having known each other since earliest childhood.
A good example of Osananajimi is Manami Tamura from Ore no imouto
Serpent boi from Demon slayer or Kimetsu No Yaiba
God he's so paranoid of Nezuko because shes a demon
Btw did I mention he's a Hashira?
He has heterochromia, which is basically a rare condition that you have 2 different color eyes
he's hot btw that's my opinion
Person: Obanai Iguro eyes are hella pretty Me: NO SHIT SHERLOCK, OFC HIS EYES ARE PRETTY