In Japanese it is common to omit personal pronouns, especially the first person and the second person. Unlike many European languages, Japanese verbs do NOT conjugate for person, so you only have the context of the conversation to judge whom the speaker is referring to. I personally find this quite confusing and I often find myself asking “are you talking about yourself or me or somebody else?”, but most Japanese seem to do just fine.
- どう思う？-> What do you think?
- これでいいと思うよ -> I think this will do it
- 昨日新しい靴を買ったんだ -> I bought new shoes yesterday
- もう知らない -> I don’t know anymore. I don’t care anymore