Vocaloids is famous?

In Japan, vocaloids is so famous. If people have never heard vocaloid songs, they would have heard the name of vocaloid.

I like vocaloid songs. So I'm happy if vocaloid songs were heard other countries.

haveの使い方 「You have come after all」、「The company has come to an agreement」といった文の「have」の役割がわかりません。 完了形なら「came」になると思うのですが、「come」ということは違うんですよね？原形だけど完了形、これだけは例外などといったことはあるんでしょうか？

Is it rude? Is it rude to response " hello " or " hi " when a teacher says to me " hello " or " hi ". " Good morning " is polite?

reply to "how are you?" Could you tell me how to reply when you are said "how are you?". Is it ok to reply about weather? For example, "today is a comfortable day."