I didn't know Kirby Star Allies has sole more than Luigi Mansion 3 (Japan only) and nearly at 1mil in Japan alone.

Looks like we can expect 150k+ next week ^^
But it will clearly lose the battle against last year's big Q1 title Monster Hunter Rise, which sold 267k.

Arceus is already the 4th big Pokemon game and many who wanted a Switch for Pokemon should already have it.

I think the only game that can create significant momentum for them on the software side is Monster Hunter (MHW2 essentially).  Final Fantasy is clearly in decline in Japan.  I doubt FF16 will have the enthusiasm behind it to even sell like FF7 Remake, which itself had disappointing sales.  Dragon Quest 12 is going to sell more on the Switch.  Other Japanese Playstation franchises are not big enough, and there aren't really that many of them left that won't consider porting their game to Switch.  That just leaves MHW2.  I don't doubt that many Japanese gamers will buy a PS5 just for MHW2.  After it releases I expect baseline sales to go up noticeably.  

However, who knows when MHW2 will release? Until then, even the best PS5 game will last 2-3 weeks on the chart, and the PS4 version won't do much better.  I believe there are a lot of Playstation releases coming up during the next month or so, but once this flurry of releases ends, the charts will quickly go back to being 30/30 for Switch.  That is kind of what we should expect from the Famitsu charts going forward.

If 2022 sells 1.3mil this quarter, it’ll be in a very good position (2021/2020 sold 1.7mil), it would need to sell around 800k for each quarter (Q2/Q3) and have a holiday of 1.5mil and that would be well over 4mil there. 2021 had an amazing H1, H2 even with OLED wasn’t as big as many would think. I have to have a comparison to show for each Half to paint a better picture 

Well, that depends on how you look at Arceus.  It's been marketed as being very different from the mainline Pokemons (even though it isn't actually the true open world game that some were hoping when it was originally announced).  That could spark interest from people who didn't have any interest in the other Pokemon games, but might have been enticed to give this one a shot.

Breath of the Wild keeps selling getting close to 2 million! Kirby getting close to a million as well.

Agreed. Almost all mega selling games in Japan are exclusive Nintendo games. And now that DQ is also on Nintendo it'll obviously be much bigger there on Nintendo than Playstation. FF is no longer the end all be all of jrpgs like it was back in the 90s and while it is still very popular in Japan it doesn't come close to DQ, MH, or the numerous japan mega selling Nintendo games. MH is the only series that will likely push crazy numbers on Playstation now and Nintendo even has their own series of that now, though World seems to be the more popular of those two MH series.

Playstation sales in Japan continue to slow down a little each gen, but software sales this gen just look abysmal. With a Switch 2 coming out likely mid PS5's lifecycle, I could see that really killing off PS5 sales in Japan because why would you get a PS5 in Japan when you can get the brand new Nintendo hybrid that is going to have almost all the popular games in japan. I think if anything Nintendo is only going to get more dominant in Japan in the future.

Kirby is very popular in Japan. Several Kirby games sold more than half of their copies in Japan. With digital both LM3 and Kirby Star Allies are above 1mil.

Next week's numbers are going to be very interesting.
Legends Arceus has the potential to reach those who were underwhelmed by Let's Go and Sword/Shield, but individual system sellers seem to make less of an impact this far into a system's life, and we're still in a chip crunch.

Surprising that the PS2 never achieved this despite selling 22million lifetime, it must have had many 3 and 4 million years. Do you know the PS2's peak year in Japan?