It is for the reverse gear shaft. Bolt part number 95801-10050-08, washer part number 90401-PG1-000. The bolt threads into the shaft. In your picture it looks like the reverse threads are not lined up.
A forum community dedicated to Honda and Acura K Series engine platform owners and enthusiasts. Come join the discussion about performance, modifications, troubleshooting, power-adders, racing, maintenance, and more!