I think Mitoma can possibly go straight to a lower level club in Bundesliga, etc. imo kinda like Keita Endo, etc. Tanaka can possibly go the Osako route and play in 2.Bundesliga or Segunda Division for a season then make a move up.
And I'm not sure what makes you believe they don't have offers. Many transfers are reported just when they are pretty much done I think it's a pretty good deal... Santa Clara has been really solid and Portugal is as close to the big 5 as you can go and we'll see what happens if he does well. You also gotta make sure that you won't find yourself on the bench at 25. I'm more wondering how they managed this financially
Heard that it was rumored to be free as his contract was running out too as well, not sure if its confirmed though.
Koki Machida is a player who could possibly be going to Europe in the future. He is under the same agency as Sakai, Yoshida, Muto, Mitsuki Saito, Takuma Nishimura, and Daniel Schmidt. https://www.transfermarkt.us/caa-base-ltd/beraterfirma/berater/674 They seem to have a bunch of pretty good Japanese youngsters with them. Including Riku Handa, Kyosuke Tagawa, Kashif Bangunagande,and Ryotaro Araki.
Already thought that Machida can give Europe a try, but still no rumors as of yet. Others like Ayumu Seko, Shunki Higashi and Daiki Hashioka, Daiki Sugioka and Taiyo Koga, etc. can also give it a try if they are willing imo. Maybe start in Belgium/Portugal or the top5 leagues' 2nd division 1st as a start.
Reported here: https://hochi.news/amp/articles/20201229-OHT1T50296.html Would be nice if we could get some cash for a replacement.