I realized that after learning Japanese for so many years I still don't know what the word is in Japanese that has the meaning "to have intercourse with" specifically.
Therefore, I am looking for a Japanese verb meaning "to have intercourse with" that:
- is not 外来語 e.g. セックスする;
- is not 漢語 e.g. 性交する;
- means "to have intercourse with" explicitly, not through euphemism;
- is not slang;
- refers to "to have intercourse with" with high fidelity (not like e.g. やる);
- should better be a 他動詞 s.t. it can fill in "A は B を _____.";
Point 5 is important, by which I mean the verb should not have other meanings, like "肏" in Chinese, "씹하다" in Korean and "fuck" in English(?). Though I am not a native English speaker and I know "fuck" as a verb has many meanings, I feel like "to have intercourse with" is still the main and genuine meaning and other meanings seem to have derived from this. Although "fuck" might mean something else before it acquired the meaning of "have intercourse with", this must have happened before people started to use the verb "fuck" in other ways (as in "to fuck around", "fuck it!" etc.) .
In comparison, やる, which is the answer many Japanese people told me after I asked them this question, seems to have too many meanings (to do, to kill, to complete, etc.).