The Resident Evil 5 demo was intended for use in Japan only, although people living in other parts of the world have been downloading it by creating a Japanese account, but the online co-op function won’t be playable as Microsoft has blocked the IPs for people living outside of this region.
The demo is rumored to be available in January for other parts of the world, but this has not been officially confirmed yet. We have contacted Capcom and Microsoft to see if we can find out when.