I watched Japanese animation!!
I watched all Digimon episodes for a month.
It's a wonderful story.
The story taught me the importance of growing your heart.
(This expression "growing your heart" or "growth of heart" doesn't really work in English, but in your next sentence it's a bit more understandable what you mean by that. Try to find an alternative such as "having an open mind" or "growing emotionally" or "being brave"...)
The main characters have grown their heart in the story.
The story is popular worldwide.
I think they (not clear who "they" is - if you mean the world, just say: "the world") sympathize with the story.
It's a day off.
It was raining until 6pm.
I like the rain's sound.
It's like silent music. (silent music is not gramatically incorrect, but doesn't make sense... do you mean quiet music?)
I was in my house the whole day.