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Shohei Ohtani and his agent, Nez Balelo , have been sued ... after they allegedly screwed over some real estate business moguls in Hawaii -- costing them a fortune.

The lawsuit was filed in Hawaii Circuit Court last week ... and in it, the case's plaintiffs, Kevin J. Hayes Sr. and Tomoko Matsumoto , claim Ohtani and Balelo sabotaged a $240 million real estate venture they had all entered into. Getty

According to the suit -- which TMZ Sports obtained on Tuesday -- Hayes Sr., a developer, and Matsumoto, a real estate broker, had gotten involved in a luxury housing project on the Big Island ... and brought Ohtani in to help promote it.

But, they allege a short time later, Balelo and the Los Angeles Dodgers superstar went to Hayes Sr. and Matsumoto's business partner,

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