When it comes to Kahoots, my students love playing them and my teachers love that they fill up the class time. But what I've found after making dozens of Kahoots these past few months is that keeping the length short is more conducive to students' learning something from the game, rather than treating it purely as a game of reaction time and guessing blindly.
LINK: https://create.kahoot.it/share/a-christmas-quiz/5ccd7c63-9734-45a4-8557-1cc7657dbc59
I adapted this from MegaTaco's kahoot from earlier in the month. I kept some of the interesting pictures and questions, but in my school's case, too many of the pop culture references would have gone over my kids' heads so I added a few questions and changed some others to get myself to 10 questions.
Save for a few exceptions, I keep my Kahoots to 10 questions, with 20-30 seconds (based on difficulty) for the first 9 questions, and giving 45 seconds-1 minute to the students to solve the final question worth double points.
I say 'Let's see question ##' before each question pops up on screen.
Followed by 'Let's see the score' when the timer runs out and I hit next to go to the leaderboard.
Just before hitting next to go to question 10, I look at them a little dramatically and go 'Next is question 10. Question 10 is the last question, so it's worth double points' (and I gesture an x and then a peace sign with my hands to show a 'x2').
Optional: Depending on your Japanese level, if there are some questions where the majority of students chose wrong, or there was one particular wrong answer that was commonly selected by them, you can explain the correct grammar, and what was wrong with the other answers that were chosen by the students. Even when explaining the more difficult questions like this, I like to keep the duration of the activity around 10 minutes at maximum.