Fascinating! Thanks for posting.
A note to the video, as some may think the number is that of the individual sub; I-400 is the sub class - not the individual sub number.
As for the plane thst some Japanese mega-subs were able to carry: Here a pic I snapped of the only Aichi M6A Seiran plane left in the world. Its from the Udvar-Hazy, which is well worth a visit IMO.
Missed the Udvar-Hazy Annex on last trip to the Smithsonian Air and Space Museum, very cool thanks for sharing.
Ive been to both and at least you got to see the 'Spirit of St. Louis' and 'Glamorous Glennis,' which fully justifies going there.
The D.C. branch of the Smithsonian is well worth a visit IMO.
If one has just one iota of aviation interest, one has to visit the Udvar - its a fantastic collection. You wont regret it, if you ever make it there. Ive been there several times and plan to go there again.
many thanks for link.