The kiss itself... isn't really a surprise, with how Gustavain has been moving, had touched him so sweetly. Thanatos isn't sure why the familiar has apparently latched onto him so quickly, but he's not really upset about it. What surprises him is the way he's kissed. Gustavain knows how to kiss him and it shows now, sliding perfectly into place where Thanatos would have expected some adjustment, a small learning curve of a new partner's mouth. It sends a shiver through him, and he lets himself fall back on the ground, hands reaching up to hold onto the body above him without fighting for any kind of control (which is absolutely what Phillip would do, didn't intentionally begin giving up control with Gustavain until their feelings were clear).

He leans into the kiss, soft and sweet, and there is something familiar about the way the elezen touches him while still being new. His hands begin a slow survey of his hips and sides, mapping out the shape of him but not reaching for more than this.