Kagami kissed them first. At separate times yes, but first all the same. The first time he kissed Kuroko was after a significantly difficult game against a well known school. They had won by the skin of their teeth and after the cheering and shouting and raw jubilation they shared with their teammates, Kagami lifted Kuroko up off the ground and into a nearly lung crushing bear hug. And in a blood pumping second of adrenaline and excitement, Kagami planted one right on Kuroko's lips as he put the shorter boy down. When they pulled away after a few seconds, both were surprised and just stared at each other before Kagami abruptly removed his hands from under Kuroko's arms. They stared at one another for a second before the team came up behind them and gave them congratulatory slaps on the back, for the win or the kiss they weren't sure, and ushered them to say thank you to the other team, and then to the locker room. They didn't bring it up again but after that they seemed to gravitate towards each other more easily and their companionship developed into an unspoken promise.
The first time Kagami kissed Aomine was after the blue haired boy's confession in the pouring rain. As they stood in that cold bus stop with nothing but the sound of the loud banging of drops against the roof, Kagami clutched Kuroko's hand tightly as he leaned in and kissed Aomine. They left their eyes open, slight as they were, and watched as their faces came in contact. It only lasted a few seconds but it was enough. All the energy that they felt from the moment they met was released in that kiss like a shotgun. The kiss itself wasn't sloppy or intense in the slightest, but it held power. Strong and assuring.
When they let go Kagami watched as Aomine pulled Kuroko to him by the small of his back and kissed the boy softly. Their kiss was different, but it held no more and no less passion than his and Kagami's had. It wiped away the doubt they had felt for each other for so long and cleaned the slate that had only held regret and longing for too much time. They went to Kagami's apartment, as it was closest, and dried off and changed and ultimately let themselves be carried to sleep by the rain and the warmth of Kagami's bed.
