That you take care of him in the same way that he does with you
Cancer loves to be in love, and with that big heart and that sensitive spirit, it was not surprising. It is true that many times you can deny your condition; you can say that you can live without love, without spark, without those butterflies in your stomach. But deep down, without that, it would not be Cancer. The Crab is linked to love, no matter how much they say otherwise. When they do, they fall in love vigorously and quickly and thoughtfully. They can see a future with you all the time; they can even see themselves married or with children.
They do not take relationships lightly, and they are indeed very sentimental.
It is true that of all that bubbling inside, they will say half of the half; they are likely to deny many things Crab. But in reality, it is what the Crab feels; when he meets someone with whom he is compatible, he goes for everything and gives absolutely everything. Out of fear, out of insecurity, whatever. But he prefers to shut up than give too much, and everything goes to shit.
He wants you to take good care of him, to give him the same that they can give you.
She may not open her mouth, but you will see in her actions that she has incredible details, and if you are a little wise, you will also see that she is crazy about you. Maybe he will never ask you, maybe he will never tell you anything, but he wants reciprocity, affection, and all the love you have to give him.