I think (based on what people say here) that he's afraid of a lot of things. Now that he is in the relationship, he has to keep everything in check, because he's not sure how secure their relationship is, as in, possibly, literally anything could end it. And it could be something as simple as a innocent gesture taken out of context. He's not sure, so he tip toeing around and not really testing any boundaries, being safe as possible.
But him opening up like this, actually will (potentially) clear the air and let both Anjou and Seto establish what they both want and what their boundaries are without accidently hurting each other.
See, this is what we want. Progress. A small step forward in characters becoming better characters.
Not in constant loop of BS like Rent-a-Girlfriend where the MC NEVER grows and is just in a constant state of arrested development.