I have watched 6 episodes of Kuzu no Honkai.
Since from the time I was born up until now I write this sentence, I have watched 6 episodes of Kuzu no Honkai, so it uses "have".
I had watched 6 episodes of Kuzu no Honkai.
Since the action "watch" was done in the past and I didn't repeatedly watch from time to time, it uses "had".
Which sentence is more natural and intuitive?
Best Answer
It's not actually a matter of "natural"-ness. In this case - assuming you're not stating there's a change in this number - the correct answer is "have".
This is current information, so it's present tense.
"Had" in this sentence implies that it is no longer the case so it would be used in a situation like:
So, now you've watched all of the episodes, which is why you use the past tense.
Similarly, if you had a friend over to watch the show with you, you might have a conversation like:
Again, you use the past tense because this information is no longer current.