Question: Butterfly Trainers in Japan

I moved to Japan almost 6 months ago and I’m starting to miss my butterfly trainer and i was thinking about buying but i don’t know the japanese law on Butterfly Trainers. For context: A butterfly trainer in a Butterfly knives but with a dull blade that cannot be sharpened. The point of a butterfly trainer is doing tricks and not pretending to have a real knive. I obviously wouldn’t use it in public or anywhere outside. Is it legal to buy/own a butterfly/Balisong trainer in Japan?

https://www.reddit.com/r/japan/comments/11ga1dt/question_butterfly_trainers_in_japan/