Almost forgot >< Yes you can, Yes but this jutsu is for one single rain drop so you would have to use the jutsu again, Only if the opponent has a way to sense it, its like a blade so depending where it hits it can kill, and it can pierce since its as sharp as a blade
(Ame Kasui no jutsu) - Rain Spike Technique
Rank: C
Type: Attack
Range: Short-Mid
Chakra cost: 15
Damage Points: 30
Description: The user of this technique must place chakra into one or more raindrops. As the drops of rain hit the ground they create a small sized spike of water from puddles on the ground. For this technique to work there must be water on the ground and it must be raining.
Focus your chakra into one of more drops of rain as they fall. When those drops hit the ground they become small sized spikes of water from puddles on the ground that were formed by the rain.
(Ame no Yari) - Rain Spear
Rank: C
Type: Attack
Range: Short-Mid
Chakra cost: 15
Damage Points: 30
Description: By using chakra to condense a large amount of rainwater into one place, the user creates a spear of water in the clouds. The spear can at any time be called down to strike an opponent with only one hand-seal. The water will stay in the form of spear for a short amount of time (three posts). If the spear is not used by that time it will fall uselessly as rain. The only warning this technique gives is a second pause in the rain when the water is gathered and condensed.
Focus your chakra and use it to condense a large amount of rainwater into the sky. Then create a spear of water from the condensed water in the clouds. You can call it down anytime you want with the use of one handseal.
*shows you handseal*
Within a certain amount of time the water will be in the form of a spear, after that it will turn into rain again and fall to the ground.