Hi everyone 
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I was wondering if one of you may know a website that teach Japanese but in a very playful way? 
A friend of mine saw me doing my reviews and he thought that an online tool could be amazing for his 8yo child. Bunpro is such a great tool but I can understand if a child is not very interested about doing hundreds of reviews 
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Have a nice day 
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Not quite SRS, but Duolingo is the obvious choice to me if we’re talking about kids. A game-like interface that uses cute characters and easy-to-understand sentences that are occasionally funny, and lacks the in-depth grammar explanations that most kids would never read anyway, or would get bored reading.
There’s a phone app called kawaiiNihongo that might work for children. At least it has cute anime characters and minigames and the content is more correct than Duolingo (not a difficult achievement tbh). They also make a more gamified app called kawaiiDungeon that teaches some vocabulary.
A lot of people in the Japanese learning community hate Duolingo, but I agree that is appropriate for kids. I study French on it specifically because it is like a game. It has a hidden SRS system also.
Not really SRS, but our two upper kids (now already adults) started with Hiragana Karuta (there are many free resources like happylilac etc) and then started using textbooks aimed at elementary school kids (like “こどものにほんご” and some Kumon workbooks). It requires help by the parents though since it is written for classroom teaching, but easy enough to teach with a little bit of prior language knowledge. They picked up vocab very fast, so up until middleschool there really was no need for SRS.
After that we used Memrise and made our own decks there since it is a little easier to use than Anki.
An other fun way could be something like the Marugoto online courses. I remember the A1.1 course being quite colourful and easy to navigate - bonus point: on their platform they also have a lot of courses aimed at beginners for Kana etc.
Duolingo as a concept is great for kids, but with Japanese specifically it gets basic stuff wrong like consistently reading kanji by their on-yomi in words that use kun-yomi, and for me that’s such a grave mistake that it basically disqualifies it from being recommended. People who ask for recommendations are generally not able to catch these errors themselves. It’s a different story for European languages, it’s much better for those IMHO.
It hardly gets this wrong “consistently”.
But furthermore, what’s wrong with that?
It’s how I found out there were different readings in the first place. And if a big old dummy like me could find that out, I’m sure a smart kid that’s interested and surrounded by adults supportive enough to enquire on a forum like this one will be fine.
I would let my kid play around with Duolingo any time. In fact if anyone would ask me about starting out with Japanese, I would direct them to Duo to learn hiragana and katakana, and some easy phrases.
Then -like me- they would be in the claws of the owl and never be able to skip studying Japanese for another day in their life.
803 days and counting.
Not sure if Erin’s Challenge might work? "Erin's Challenge! I Can Speak Japanese." Contents Library | The Japan Foundation Might be aimed more at middle/high school students… But at least there’s more school related vocab than business talk lol. (It’s also not an SRS, but yanno. I had to write my own paper flashcards as a kid, but I also hated language learning back then…)
For me it was really consistent. For example, when the word bank split kanji from okurigana, I got onyomi readings for the kanji, e.g. it would read 来ます as らいます. 100% of the time. I’m sure people can figure this out in principle, but it’s really difficult to get rid of bad habits learned early so I would never give this to a child (or an adult) who’s being exposed to Japanese for the first time.
I LOLed 
People seem to have made up their minds. 
Why would you force a child to start doing this?
Very inhumane!
But also, you could just try throwing a genki book at the child several times. That is how kids learn trust me I am a reliable source.
Lol’ing at the thought of a toddler sitting down to do ghost reviews. Anyways, not to pry too much into the life of your friend, but would their partner happen to have some level of Japanese language skill? Or do they themselves have some level? I think that would pretty significantly change what kind of tools/content you’d be able to throw at them because then you’d be able to do a bit of teaching instead of solely relying on the medium itself to drive the point across to the kid.
@rikvg What is life like on Duolingo after 800+ days? That’s an awesome feat nonetheless! I’ve had friends do various languages on there but usually stopped after ~2 years due to burn out and they felt like like they were near the end of it’s capabilities. I briefly tried out Duolingo for German and Japanese but I don’t think it was a good fit for me personally, but I’m glad people find success with it!
I would probably suggest Lingodeer over Duolingo, but I know it went a bit more on the paywall-y side a few years after I stopped using it often. I don’t know how viable an option it is now or how much it’s changed… It was more consistently accurate than Duolingo though, and I think the deer is way cuter than the owl that haunts my nightmares.
First, thanks everyone for all your replies 
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At first I don’t wanted to talk too much about his life, but if it can helps to answer my question:
My friend recently broke up with his Japanese wife. So she was in charge for teaching Japanese but now the kid will be most of the time with him so I think my friend would be glad if his son could continue studying Japanese while with him (my friend never learned Japanese).
If the child already has 8 years of native japanese education under its belt (assuming the mother spoke her native language to the child), there really is no need for SRS. The basic vocab should already be there and just needs to be kept active.
The key would be not to let the child „forget“ the knowledge it already has, so native material like anime, manga, tv series and maybe 一年生/ 2年生reading stuff will help. If possible, your friend could also reach out to a japanese community near him or join Hafu groups (facebook has a really active community!) for more resources and maybe help to connect kids in the same area with a similar (language) background and same age as the child.
It’s mostly bunpro light now. I finished the Japanese course (everything to level 5) in under a year. They added an extra “master” level with the hardest exercises of every item and no hints, and I am doing that very slowly. Also levels “crack” if you haven’t repeated them in a while. This keeps you engaged to keep repeating stuff.
The most practical use I get out of it is that it is yet another context (besides reading, BunPro and Wanikani) to encounter vocabulary. I am 47 years old and spent half my life in bars so my memory isn’t the greatest. Any chance I get to repeat stuff, I take.
I spend about ten to twenty minutes a day on Duolingo now. So it’s not a big effort.
And the other half was wasted… 
to paraphrase George Best
Same, same. Retention is really difficult.
Those are good recommendations. As a matter of fact Kawaii Nihongo was the first experience I had as a learner of the japanese language. I really like the vibes the app is giving, but things did not stick so well with me, so I moved on. I also think the app is more geared towards Weebs than children, as the mascot is a cute anime girl, rather than a cute animal. Though Cute Girls and Princesses usually work well for girls, but not so much for boys of that age.
There are other playfull apps on Google Play as well. One I can name is infinite japanese, which is vocab only, but works fairly well to learn the sounds of each word and its meaning, less so its reading.