Covering the 2SK2381, this 394 KB PDF is catalogued as a schematic, but the part number follows Japanese JIS naming where 2SK identifies an N-channel field-effect transistor, so expect a datasheet. The name states nothing else. Open it with any PDF viewer to read pinout, absolute maximum ratings and characteristic curves. These figures guide selection of an equivalent part when the original has failed, and the package marking should always be checked against the number first.
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.