In "Kindaichi the Killer," Ryuji Saki, who very much resembled his elder brother, Ryuta Saki, approached Kindaichi at a party, telling him his elder brother told him in a dream that Kindaichi would be in trouble. Soon after, Ryuji helped Kindaichi avoid a murder rap. Afterwards, Ryuji claims himself as Kindaichi's assistant and sometimes really helps Kindaichi in solving cases.

(Source: Wikipedia)