A stone drops from the sky into a rice paddy and then a cross drops on top of it. They've combined to form a tombstone! Wait, does that mean a body fell from the sky first and you just didn't see it?
Now you're curious about what's under there but when you try to touch the tombstone it's radiating with intense heat (ひ)! It must have come from outer space and this heat is from when it entered our atmosphere!
Currently there are no similar looking kanji which exist in the WaniKani learning system