Although they will state that they have nine satisfied native English teachers employed with them, this is far from a good choice of employment options if you want to work in Tokyo.

I have only been interviewed at their office which is the upstairs floor of the owner's home in a suburban house 30 minutes outside of Tokyo (with a dilapidated interior (read) stained and peeling wallpaper).

I arrived on time for my interview and was made to wait 25 minutes because they were behind schedule with their interviewing activities for that day. No apology offered.

I will try to paint a clear picture for you about that interview. Walking through the upstairs front door, I then was placed at a dining table with two other interviewees.
We sat in silence while another interviewee (in the same room and not more than 3 meters away) was interviewed with the boss sitting behind the lady who interviews prospective teachers. The boss can't speak English so he speaks to her and she awkwardly translates/explains what he wants to know.

They asked me questions and clearly showed that they had not read my resume. Then, a quick interview was followed by my viewing of a copy of the "contract" which was their copy on an aged B5 sheet that looked like it had been written on an old typewriter.

The so called "contract" only had items that were in the employer's interests. The first item on the contract explained that a teacher would be docked 10,000 yen per month (redeemable at the end of a 12 month working contract) because they worried that each teacher could be a flight risk.
That is a hint that they do not trust their teachers from the get go and they will never advertise this fact in their job advertisements. It is a red flag guys!

Numerous other items/clauses stated reasons why the company could penalise a teacher for any number of reasons.

A shocking contract item basically allowed them to not pay if it suited them, e.g. if they were unhappy with your work.

Another item in the contract stated that a teacher must give a notice of 60 days if they wish to discontinue working there.

Japanese labour law stipulates a requirement of a notice of 14 days for full-time workers, while it is common courtesy to give a notice of 30 days prior to leaving.

No mention about pay scales in the contract but they proudly advertise the pay is 250,000 yen to 300,000 yen. This is not the full picture because when you start, no matter how much experience you have, you will start at 250,000 yen for full-time work MINUS the 10,000 yen monthly deposit in case you quit before your contract is finished = 240,000 yen. That 300,000 yen is a pipe dream.

Also, they will ask you personal questions relating to you have a Japanese gf/bf and do you live alone, etc.

Forget about asking about National Health Insurance coverage.
They avoided talking about that with the interviewee before me and then they brushed it aside with me, saying that they would discuss that kind of thing in the second interview, if they choose to invite you to a second interview. A high-handed approach on their behalf.

Do you really want to put yor working future in Tokyo in the hands of Mr. Kobayashi (the owner), well please think twice.

This is a second rate operation and they don't trust their workers. It is clear.

And that was only the interview, lol.!