Hello I figured it would be best to post this in English and Japanese both. In version 1.5.4 I accidentally introduced a bug that made the game sometimes impossible to clear without getting hit due to making the stage 2 skellycow enemy (the skeleton cowboy) invincible.  The skellycow produces "random bullets," so if you do not clear the enemy quickly it makes it sometimes impossible to not get hit. Please update to version 1.5.5.  Thank you. 

1.5.４のバージョンでバグがあります。ステージ２で「skelly　cow」はインヴィンシブルです。

1.5.5にバージョンアップしてください。すみません。