Do all mifi’s work on the ONC mobile one?

I discovered tonight the ONC mobile one sim card. I think it's a perfect solution to staying in japan for a couple of months.
I am wondering though about mifi devices. If i purchased one on ebay, or even amazon japan, such as the Huawei E5220s-6 (listed on ebay as "unlocked", etc) how do i know it will work with the onc? do all mifi's work with this sim?
thanks!

Only ones that are compatible with Docomo's LTE and 3G network. Btw, I'm not sure what you plan to use it for, but the OCN sims are throttled to 200kbps, which is pretty slow for most things these days. Streaming and some services like voip or video chat might be unusable.

it is throttled for the one month 7 gigabyte plan but much quicker for the one month Two gigabyte plan. Do you have an alternative in mind? I will be there for 3 months.also, how do I check if it is compatible with their 3G?

it is throttled for the one month 7 gigabyte plan but much quicker for the one month Two gigabyte plan.

Whoops, I made a mistake. They're throttled to 200kbps once you've hit your cap. The 2gb and 7gb plans are offered at 150Mbps and 500kbps respectively, but it looks like you'll need an LTE router to take advantage of the higher speeds. The Huawei E5220s-6 appears to be 3g only.

also, how do I check if it is compatible with their 3G?

Check that it is able to operate on the 2100Mhz frequency.

i appreciate the help very much.
Seems like it is very worth it to get a 7gb sim, and just use it for maps, email, and general web browsing. I can use wifi for any video watching.
I am wondering though, I posted a question regarding wi2: Seems that if you sign up on the japanese version of the wi2 u300 site you can get a monthly plan for like 400 JPY. Is this so?
Any other way to get on the wimax? I am basically just trying to cover myself coveragewise for the 3 months i'll be there without dropping 700 bux on renting from the price-gouging rental services.
Thanks!