The match was the first since sport in Japan were suspended for four months due to the Covid-19 outbreak
Harambee Stars striker Michael Olunga was in action for Kashiwa Ryesol in Saturday's home loss against FC Tokyo.
Olunga, a trusted goal hunter for Kashiwa Reysol, did not manage to find the back of the net as they went down 1-0 at Sankyo Frontier Kashiwa Stadium.
Japan's J1 League resumed with nine matches staged on July 4.
Tsuyoshi Watanabe scored the goal that separated Olunga's side from their visitors in the 62nd minute with the assist coming from Masato Morishige.
The loss saw Kashiwa Reysol lose ground with the leading sides as they have now dropped to the eighth position on three points following their win in the J1 League opener.
Tokyo are second after winning both matches of the season and their inferior goal difference puts them behind Sanfrecce Hiroshima.
The J1 League had been suspended after only one match had been played.
After the competition was halted, Olunga revealed his worry that it may affect his goal scoring form.
“I had scored against Gamba Osaka in the J-Cup and then scored in the first league match of the season and then the games were stopped,” Olunga explained in an earlier interview.