Simplify the following text for a Grade 7 native English-speaking person.
Original: The use of `` Sailor '' comes from a style of girls ' school uniform popular in Japan , the sÄ `` rÄ fuku ( `` sailor outfit '' ) , on which Takeuchi modeled the Sailor Senshi 's uniforms .
Simplified: They are also young Japanese girls . Their real names are not Sailor Mercury , Sailor Venus , Sailor Mars , and Sailor Jupiter .