Hi,
we are planning our travel to Tokyo but we don't know exactly where to stay during the conference.
Is it better to find a place near the conference venue, or maybe move to another district with more things to see/do after an hard conference day?
Does anyone has already planned where to stay? Any advice from the organizers?
Tokyo is huge and the conference location is a bit out of Toyko...I,recommend to,look,for,something in the conference area..if you have some extra days then move to the Tokyo center...well there is no center...I spend my extra days in Shinjuku and Shibaia.
Look for hotels near Kamata station...best east of Kamata station in order for being close to the conference location. Of course you can stay outside Kamata but as said, Tokyo is huge, taking the metro is challenging if you are new to Toyko. And the accommodations near Kamata are actually affordable compared to areas like Shinjuku...Tokyo can be very expensive but you can find often some decent locations for a reasonable price...double check if you book a smoker or non-smoking room...also i found various hotels offering dedicated rooms for females only.
Thanks, you confirmed my doubts.
Ok, i'll watch around kamata station for conference days
I prefer to be close to the conference center during the conference—within walking distance if it is affordable, else near a transportation hub—so that I can minimize travel time and have more time to spend with colleagues. It's nice to be able to drop your laptop or grab a coat or change clothes at your lodging, then meet up wherever the crowd goes nearby.
Before or after the conference, vacation!
Yes, that's also my idea.
A second (hidden) purpose of this topic was to understand if most of the people are going to stay in the same area, so it's easy to meet and hang out together 
Now i need to understand if it's better (for the high places) to take some vacation before or after the conference.
UI
I just does not make sense to stay at some random place in Tokyo because the area is pretty huge and Kamata area is a very southern suburb of Tokyo and already in the middle of Tokyo and Yokohama. I've been to Tokyo and Yokohama last year and it really does not make sense for staying in the "core" of Tokyo...public transportation is excellent but the distances can be large and travelling with the metro or trains during peak times can be annoying...so stay close to Kamata - at least for the core conference days.
Also Haneda airport is close to Kamata (unless you arrive on Narita airport).
Completely off topic, but maybe useful anyway:
Tokyo (and a lot of other places in Japan) can be booked up quite a bit in advance (more than almost any other place).
If you are stuck (or for the vacation part), both dorms and capsule hotels are OK (japanese people are very polite and not making much noise etc (so most turists behave very well, too).
There are two different metro companies (maybe more), that runs a bit 'parallel' (but you can buy a more expensive ticket that can be used on both if you can not figure out 'where the different run) and out of 'centre' the information is in Japanese, so Maps.me or something similar is very useful.
The metro stops 'rather early', so if you go drinking you might have to stay up until morning 
or take an expensive taxi
What you want and need it a PASMO smart card which you can buy at any station or kiosk.
-aj
the other option I used a lot on my last trip is business hotels, either small local ones (what I used in ebisu, tokyo), or chains like https://www.toyoko-inn.com/eng/search/detail/00020/. They are basic but given prices are high for hotels its fine. If you are european think Formula one (but not shared bathrooms and plastic like F1).
I haven't booked anything for Tokyo yet though. Seems like some consideration is going to be needed as to where the drinking is going to happen first