I'm looking for an old cartoon, it aired on TV2 in Malaysia dubbed in Malay around 2007 ish.
Story wise it took 'inspiration' from Ultraman heavily. It was about a crystalline alien running away with some kind of weapon and crashing on Earth in a construction site. A kid got in the middle of a fight between him and another alien and almost gets killed, he combines with the kid to save his life and transforms.
It was an episodic monster of the week story, a different alien appearing and being fought every week. I do remember partway through the series, the alien dying and the kid gaining the ability to transform into that form by himself.
I remember it was a somewhat Asian setting as the kid wore a school uniform with a white shirt.
The hero alien had a red colour scheme. The weapon was a crystal thing that allowed him to use different colours of crystals, I think they were supposed to be elements. As far as I can tell, the kid gained the ability to transform by himself by using that crystal. They were stuck in the same body. Kid felt generic? if that makes sense, brown spiky hair is the main physical characteristic I remember.