Shin SOS Dai Tokyo Tankentai
Japanese title: 新SOS大東京探検隊
Type: Movie
Episodes: 1
Source: Manga
Genres: Adventure
Studios: Sunrise
Producers: Bandai Visual
Duration: 41 min
Rating: PG-13 - Teens 13 or older

"While packing for a move, elementary school student Ryuhei finds his father's old school notebook detailing a search for a treasure in Tokyo's vast network of underground passages. With his little brother tagging along, he and three friends from an online chat room gather and set out on a quest to find the treasure. What they discover instead is an entire underground community composed of assorted eccentrics, including a senile old soldier still performing a World War II-era mission."

(Source: ANN)