Diabolo suicides are tricks where you let go of a handstick & catch it again in some way. The inside wrap suicide is very different from a Straight Suicide, in this trick one handstick is thrown so that it swings around the diabolo before being caught again. This move can also be performed on both sides.
Spin the diabolo. Choose which stick you want to release then shift your grip on that handstick so that you are holding it upside down in a fist. The handle should be poking out the top between your thumb & index finger & the tip should point down towards the diabolo. Raise the other handstick straight up in the air so that your fist is halfway between the diabolo & your raised hand.
Gently throw the lower handstick inwards over the top of the diabolo so that the stick passes between the string & your body. Don't throw too hard, if you do the handstick will jerk & flap about as it swings round the diabolo making it harder to catch. All you need to do is get the stick to swing in a smooth arc. After letting go, reach down with your empty hand holding it open with your palm facing down & inwards ready to make the catch. If you use a long string (or have short arms) you may need to stretch your other arm up a bit further at this point so that the swinging handstick doesn't hit the ground. Catch the swinging stick in a normal grip & bring it back up to waist height before the diabolo rolls down the string & crashes into it. After the move you should finish with both sticks at waist height & with the string wrapped around the axle. Unwrap by circling the handstick that you released around the cup closest to you.
A nice simple sequence including this trick is a Straight Suicide letting go of your dominant handstick, which ends with your hands in the correct position to do an inside wrap suicide then exit with a Chinese Whip or an Outside unwrap suicide. You can also throw the handstick so that it passes in front of the string rather than between it & your body, so that when you finish the move you need to unwrap the diabolo with your subordinate handstick around the cup closest to you. While the appearance of the trick doesn't change it opens up your options for which trick you can perform after the move.