Bitter Choco Decoration depicts a shy person who eats away at their self in order to fit in with their company, and in the end, they're just a hollow shell that's just bitter and hateful.

The servant doesn't show up to serve food at 2:59 because the master had already eaten up their individuality. There is nothing left to serve to their master.

At 3:08 the master looks lost, with a vacant look in their eyes when greeted by one of their friends. A malevolent distortion of the master's self flickers at 3:15 presumably because of their bitter regret in changing.

The master's friend unintentionally reopens old wounds when they say, "Now I remember! You’re the one who always seemed super serious- Never mind, forget I said anything".

That's just how I interpret it though.

I liked it mainly for the animation, it's what makes the song interesting.

This lyric page tells it better.

Everyone woke up late. Jeffrey, our dog, somehow opened the cabinet and is now licking the remains of a peanut butter jar off the floor. Please be dog friendly peanut butter.