When i originally tried GBF i used my usual email to register, but then i stopped playing and cancelled the game because i wanted to wait for the english patch.
Problem is, i still receive daily emails from info@mbga.jp..... is there a way to cancel my registration? I've tried to click on a link at the bottom of their mails that talks about it but they ask me for a Yahoo Japan ID.
I know i could simply block them but i'd rather erase the account cleanly.
You are using some words out of context, so it's unclear what you did or want. For example, you say you "cancelled" the game... I have no idea what that means. Did you uninstall the app from a phone? It's a browser game, so that doesn't really affect anything.
Also, even if you erase all records of a Mobage account, that doesn't mean you will be removed from their mailing list, they are technically two separate things (although it might affect the nature of content you are mailed). There is no such thing in the world of spam as "erasing an account cleanly" I'm afraid.
Mobage likely has a few different mailing lists, so you'd need to remove yourself each time you get a message from them. It would be a long process, but it sounds like you already found the link to do so.
Ultimately, the thing I find most confusing is that you say the whole reason you wanted to stop was to wait for the English patch, but that's only 5 days anyways. Is it worth messing around with accounts and such for that span of time?
What I'd recommend is to create a filter to have all their messages flagged for Granblue, then skip the inbox and archive. That way, you have some record of them in case they give out codes you want, but you never have to see them unless you look for them.
I'll try to clear up the confusion: I cancelled the game from my computer (Chrome Apps), i never installed it on my phone in the first place. And i actually stopped playing about 2 months ago, it's just recently that i got tired enough of the mails to come here for help :V
I guess i'll follow your advice in the off-chance they actually send me something useful (although since i don't know a word of japanese Google Translate will get a workout....)
Not sure if any of the mods still support this community, but they should be aware that the forums are infested with bots and that their forum needs to be upgraded.