Not to be a filthy shipper on main, but Date/Aiba gets me ARRRRRRRRRRRRRGH [smashes my horns against the wall.]
On a surface level, their dynamic is hilarious. They share quite literally one braincell. They're a tsukkomi duo! Straight guy and dumb guy! It's peak comedy!
A bit deeper, they're repeatedly stated to be extensions of each other. Aiba is quite literally a part of Date's brain. They share thoughts, perceptions, dreams. When Mizuki psyncs into Date in her route, Date appears with a golden eye despite not being wearing Aiba physically at the moment, because he is incapable of picturing himself without her anymore. Aiba was literally made for him. You can't take Date out of Aiba any more than you can take Aiba out of Date. They speak in cypher, in lies and concealed truths, but they're incapable of truly hiding anything from each other. I hate you, and I never want to see you again. For all their banter, all their teasing, they know. They know exactly what the other mean at any given time.
And even deeper than that, Aiba and Date trust each other with their life. Aiba handed him her self-destruct code. She didn't have to do that! He literally did not ask! She could have stuck to "yeah I can self-destruct" and that's it. She offered that to him. She handed her life to him. She trusts him, completely, with her entire being. If there is such a thing as soulmates, that's what the two of them are.
Guys who are not dating but nonetheless married, bottom text.