Analysis

Since I ran with my GPS recorder (Garmin 910XT) yesterday, I analyzed my performance during the race after I got home. The recorded distance (each 1 km) included my meandering in the course, so it was always a little shorter than the certified distance displayed on the road. I corrected my pace in accordance with the certified one.
My plan before the race was that keeping 4m50s/km from the start to 35 km, 5m20s/km to 40 km, and 5m40s/km to the end. My actual pace was not too bad, staying constant except for the time loss going to the toilet and slowing down caused by fatigue and bad condition after 35 km. The split time of the first half was 1h40m52s and that of the last half was 1h42m55s. These were much closer than I expected. Anyway, I never walked, and it was the best race I've ever run.