Grammar often used but not seen in textbooks: ～かなと思う/かと思う

1. Why should we use "～かなと思う"?

Using "～かなと思う" can make your tone softer.

In N5 or N4, the teacher taught us that 「~ と思う」 means "I think."

But a significant problem that the teacher did not mention is that 「~ と思う」 means 100% subjective.

This means that this is what you think with intense subjectivity, no matter the objective facts. Then this may lead to an argument.

For example,

同性婚について、多様性が求められる現代社会では認められるべきと思います。（100% subjectivity）

As for same-sex marriage, I think it should be recognized in a modern society that demands diversity.

同性婚について、多様性が求められる現代社会では認められるべきかなと思います。（95% subjectivity or uncertain）

This is not uncertainty but avoiding conflict. Politicians, Internet speakers, interviewees, and so on often see this form of speech.

2. What about "~かと思う"?

Example Setences:

A: 山田さんはあとどれぐらい来ますか。

B: そろそろ来るかと思います。

このコラムを読めば、きっとご理解いただけるかと思います。

お忙しいかと思いますが、ぜひご参加ください。

A: この料理、前回食べたときの味と違う。

B: もう少し牛乳を足したらいいかと思うよ。

It is the same as "～かなと思う," but it is more subjective in expression, and it is also 95% subjectivity.

Why do I say that "～かと思う" is more subjective than "～かなと思う"?

You see, "～かな" is only 50% certain. After adding "と思う"  to "～かな," although it is 95% subjectivity, it may also be really uncertain. 

3. In Conclusion

～と思う→100% subjectivity

～かと思う→95% subjectivity

～かなと思う→95% subjectivity or really uncertain

コロナと思う。 I think I got COVID-19. (100%)

コロナかと思う。I think I got COVID-19. (95%)

コロナかなと思う。I think I got COVID-19. (95%,uncertain)

This is a unique feature of the Japanese language.