Sheet finishing apparatus and sheet finishing method

An image forming apparatus comprising:

• a scanner that reads an original document;
• a printer that prints an image read by the scanner on a sheet;
• a discharge opening from which the sheet printed by the printer is discharged in an operation mode other than a manual stapling mode, and into which a bundle of sheets is manually inserted in the manual stapling mode;
• a stapler that is disposed inside the discharge opening and binds the bundle of sheets inserted into the discharge opening with staples;
• and
• a transverse alignment plate that aligns the sheet discharged from the discharge opening in a sheet discharge direction in the operation mode other than the manual stapling mode, and guides the bundle of sheets inserted from the discharge opening to a position of the stapler in the manual stapling mode, the transverse alignment plate emitting light or exhibiting fluorescence.