Simplify the following text for a Grade 9 native English-speaking person.
Original: The core martial art from which aikido derives is DaitÅ - ryÅ `` aiki-j Å `` jutsu , which Ueshiba studied directly with Takeda Sokaku , the reviver of that art .
Simplified: Aikido is based on the martial art of DaitÅ - ryÅ `` Aiki-j Å `` jutsu , but began to separate from it in the late 1920s , partly due to Ueshiba 's involvement with the Å moto-ky Å religion . Ueshiba 's early students ' records use the name aiki-j Å `` jutsu .