You don't disappear — you just slowly become a background character in each other's stories.
It happens over weeks. Maybe months. You start replying slower. The plans get vaguer. You're 'really slammed right now.' You're still there — just less there. Less warm. The other person probably senses it. You probably know they sense it. But saying it out loud feels like detonating something when you could just let it dissolve. You tell yourself it's kinder. Sometimes it is. But mostly it's a way to avoid being the one who officially ended it — to let the ending happen to both of you instead of being the person who caused it.
Get your read — free on iPhoneyou fade while still being technically present — because saying it would make it real, and you're not ready to be the villain of that moment.