I have read about the duck in AoS somewhere stating that all Konami games for that year had a rubber duck somewhere, including that year's metal gear game (forgot what that was).
As for the translation, here it is:
Duck and I
Hello. I am Yadabon, the character designer. Thanks for buying Drac68. I am now in the middle of bug checking and it is very difficult~~~~. The rest of the team said that I am the worst player. Thus it took me 3 days to defeat Dracula in such a hard environment. I had a philosophy that I can do it, but now, I am in tears. Bwaaaah....
You users might say that I am weak since it took me 3 days to defeat 6 stages. It's ok, ok... boohoohoo... By the way, on my 6th round, did you see the abnormal phenomenon that was caused by the goddess of Block 4? Blood...Blood... For those who did not, it's best to keep silent.
While the game was in development, I bought books, watched horror videos in order to capture the imagery needed but I remembered that I can't handle horror movies, thus there were times that I did not even finish some of them. That was not helpful after all. What I meant to say was, scary things are scary,scary,scary. I remembered a scary memory. I hate of ducks. It is because if you kick the previous duck, they will instantly chase you at lightning speed. I fear ducks more than Dracula.
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There you have it. The reason for the ducks.