You think for a minute and then reply to Matt's message. "Can't come now, another time." You put away the phone and feel your borrowed body up. Jacob and you don't spend that much time together. You mostly spend your time in your room, gaming with friends you've met online, while Jacob goes out a lot and hangs with his friends. So, even though you've become your big brother, you might as well have possessed a stranger. You get up out of the bed and walk over to the mirror in Jacob's room. There you look at your new self and start to take off your pajamas. First, your shirt comes off, revealing Jacob's quite muscular chest and arms. Then, as you start to pull down your pants, you seem to experience some resistance from the growing bulge in your underpants. You pull down your pajama pants and throw them aside. Looking at Jacob's body in the mirror makes you smile. You flex a little with your new muscles, grab your crotch and squeeze it a bit.
One of your hand moves slowly into the underpants. A wave of pleasure overflows you as you gently stroke your brother's dick. Looking into the mirror you see Jacob, staring at you with a horny face, asking for you to continue what you're doing. By increasing your speed, your pleasure also greatly increases, causing you to bend your knees and close your eyes. The longer you pump, the more natural it starts to feel. It feels like you're no longer just Tom inside Jacob, but like you are Jacob. You take off Jacob's final layer of defense and throw the underpants onto the floor. "Unggg....." The moment of truth is closing in and you let yourself fall onto your knees. You can feel the warm cum running through your dick under great pressure. As the cum reaches the head of your dick you are filled with pleasure and moan out loud.