Ishihara was the key man as Sanfrecce secured a 3-1 win over second-placed Omiya on Wednesday as the battle for the title intensifies.
The striker struck after just four minutes to give the hosts the lead, but Omiya looked to have earned a point 74 minutes in when midfielder Daigo Watanabe levelled things up.
Ishihara was not finished, however, the 28-year-old netting nine minutes from time before making sure of all three points with his third in the 94th minute.
Yokohama F. Marinos stay third, but they could only manage a 1-1 draw with Kashiwa Reysol, Marquinhos' 31st-minute penalty cancelled out by a an 89th-minute own-goal.
Urawa Red Diamonds are a point behind following their 2-1 win at relegation-threatened Jubilo Iwata, defender Ryota Moriwaki scoring an injury-time winner after Marcio Richardes had tied things up following Yuchi Komano's opener for the home side.
There was disappointment for fifth-placed Cerezo Osaka as they slipped to a surprise 1-0 loss at Albirex Niigata, Kentaro Ohi netting in the 72nd minute.
Ventforet Kofu fell into the bottom three by virtue of their 1-0 home defeat to Vegalta Sendai, Brazilian forward Wilson scoring the only goal of the game after 22 minutes.
Kofu's slip-up allowed Shonan Bellmare and Sagan Tosu to edge away from the drop zone with wins over Kawasaki Frontale and Oita Trinita respectively.
Shonan had to come from behind to secure success at Kawasaki, Wataru Endo and Kaoru Takayama finding the net in the second half after Yoshito Okubo had scored his 13th of the campaign just before the interval.
Meanwhile, Sagan won a 3-2 thriller against Oita thanks to a late winner from Diego Ambuila.
Akihiro Sakata put the visitors ahead after 40 minutes, but Kei Ikeda levelled matters 11 minutes into the second half before a Yohei Toyoda penalty on the hour mark put Sagan in control.
Daiki Takamatsu brought Oita back into the game just two minutes later, but Ambuila struck 14 minutes from time.
Nagoya Grampus were 3-1 winers over Kashima Antlers, Australia international Josh Kennedy netting a double while 33-year-old striker Keiji Tamada also scored to wrap up a comfortable triumph.
Elsewhere, Shimizu S-Pulse played out a goalless draw with Tokyo.
