You find Lambo passed out and barely breathing. Broken glass from god knows where, bullet holes in the walls, and a pool of blood surrounding the boy. What a mess.
Leave it to Lambo to screw up such an easy mission. Tsuna should've known better, and if you're going to be really honest with yourself, you should've known better. The mission had been so easy though, child's play. Just steal a few files from the Russo family, a rival of the Vongola. That was it.
The cow was stupid though and hadn't watched his back. From the looks of it, they had snuck up on him, shot him, and taken the files back. You do take an odd satisfaction in the scorch marks throughout the room. They're from electricity, at least the cow went out fighting.
You could easily leave him. He's not going to die anytime soon and it should be the Bovino family's job to clean this up anyway. You tell yourself that it's just on a whim that you lift him up carefully and carry him out, drive him home.
If you're honest with yourself, you know deep down that the boy is getting to you. He's chipping away at the cold rock that is in the place your heart should be to make a soft spot for his annoying little self. And just maybe your letting him do it.
But you've never been quite that honest with yourself. So when you get back to Vongola headquarters, you lecture Tsuna on letting the Bovino boy go on a mission of any sort of importance. When the cow asks you why you saved him, you make up a logical excuse of not wanting to step on the Bovino family's toes, because really, the Vongola family has enough to worry about these days.
A few days later, the Russo family has mysteriously disappeared from the face of the earth.