Shinji knows that a lot of this is for his own peace of mind. Having Kai solidly here, in his arms and returning this spot of affection, is always going to offer him a moment of quiet assurance. With that in mind, he was also fairly certain that Kai was in need of the contact as much as he was. It's a simple action, but one that Shinji hopes communicates well enough that he's Here, he isn't going anywhere, and that the two of them should be okay. A good baseline to convey before trying to dive into putting words to all of his feelings.

He sighs gently, sinking into the embrace and tightening his own hold as Kai's arms envelop him.

"I just need to do this for a bit," however long this 'bit' might be. "It's easier to think about this with you right here."