Titled 2SK2378, this 26.7 KB PDF is the smallest in its series and is listed under schematics, but the JIS part number indicates a datasheet for an N-channel FET. The file name offers no maker, package or revision. Expect a compact sheet with pin assignment and key ratings. It helps when replacing a failed transistor: confirm gate, drain and source positions, then make sure any equivalent has at least the same voltage and current capability.
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.
Any PDF readerSumatraPDFFirefox / ChromeFlexBV (links PDF to boardview)