leaving Japan with visa in old passport?

I have just got a new passport (UK) here in Tokyo as my old one was full up with visas.

Is it absolutely 100% essential that i need to go to the immigration office to transfer my current valid tourist visa to my new passport, or can i simply present both passports at the airport when i leave.?

(the old passport is still in date and has just small corners of pages cut off except the Japanese visa page)

any help and experience very much appreciated especially if it saves me the laborious trip to immigration.

Thanks.

Present both passports at the same time; I have done it for a different country and that always worked.

I support to present both passports when you present for immigration clearance. Some countries attach both passports together upon request when the new passport renewal application is submitted.

If you read to the end of this from the ministry of japan. you will see you have to transfer it.

If the holder of a double-entry or multiple-entry visa obtains a new passport while the visa is still valid, he or she can have the visa transferred from the old passport to the new one at an embassy or consulate. (The Ministry of Foreign Affairs in Japan does not handle this business.) Please note, however, that in this case the double-entry or multiple-entry visa in the old passport must still be valid.
In the case of foreigners who have already completed entry procedures and have temporarily departed from Japan with a re-entry permit from the immigration authorities, there is no need to transfer the visa to the new passport for re-entry into Japan, because the original status of residence in Japan is considered to be still valid.

Note: In the above case, foreigners residing in Japan, when they obtain a new passport, must have all valid stamps (e.g. landing permission, stamp of permission to extend their period of stay, stamp of multiple-entry permission, etc. obtained from an immigration authority under the jurisdiction of the Ministry of Justice) transferred to the new passport. For more information about transfer procedures, and/or inquire at the nearest immigration authority.

Jesse, the OP doesn't have a reentry permit and he doesn't live in Japan. He simply has a tourist visa and is leaving Japan for good. He doesn't need to do any transfers.