Blachu or Blake as he's later known as was supposed to be a clone of Sonichu but due to an accident Sonichu's DNA combines with a splash of Cherry Cola, creating Blachu.

He starts off as a villain and a rival to Sonichu but eventually becomes one of Sonichus friends and allies.

For Blakchu I imagine his voice being a little breathy and sounding similar to a brooding anime character. If you want though you can also audition for this character doing a Shadow the hedgehog impression. It's up to you!