Reference sheet for the 2SK2599 in a 418 KB PDF, placed in the schematic section although the name holds nothing but the part number. In the JIS scheme, 2SK identifies an N-channel field-effect transistor, so this is most likely the maker datasheet with ratings and curves. It helps confirm the pinout before probing, establish voltage and current limits, and select a substitute with compatible gate threshold and package. Inspect the marking on the actual component to be sure it is the same type.
The button opens the matching file on RM Schematics, or a source page if it is not catalogued there yet. The original attachment is from @cyberlanelectonik. Enginerys does not host this file.
How to open a .pdf file
The standard format for schematics, block diagrams, power-sequence charts and service manuals.