This is a glitch that allows you to easily clear the Gamakatsu fishing contest event held every Sunday.

There are two conditions.

First, it must be an initial ROM. (So this glitch cannot be done on Switch or Steam)
You can't tell from the outside whether it's an initial ROM or not.
You can determine if this glitch can be reproduced or if the ROM hash value is below.

The ROM hash value is below.(SHA1)

Initial ROM : c0236a787207e09e61ae71801d712a638f7e2776
Late ROM : 97a52b39dbddebe097613e847041a19df6d12ce8

The second method is to reproduce it in-game.

1. Challenge the contest by bringing two or more baits. However, you must reduce the amount of food to 0 during the contest. So around 3 would be best.
2. After catching 2 or more fish during the contest, set the bait to 0.(Trash is not counted.)
3. Wait until just before the contest ends with 「餌がありません」(There's no food.)'s line. The contest time continues while the lines are being given. Use the movement of the hourglass as a guide. (The internal clock must be less than 100 at the moment you send the message.)
4. After the contest ends, press the ○ key at the 「がんばってね」(Good luck) line. (At this time, the internal time must exceed 100.)
5. If you succeed, the bell will ring again and you will have caught 50×n fish. You can also receive 50×n×50 Yenom. (n is the number of fish caught)

Although it is in Japanese, the explanation video is below.