Well, typically, a Hellsing manga box set includes all the individual manga volumes of the series. It might also come with bonus content like character sketches, author notes, or maybe even a limited edition figurine. The specific contents can vary depending on the publisher and edition.
The Nana manga box set usually contains multiple volumes of the Nana manga series. Sometimes, it might also come with special extras like posters or collector's items.
Try looking at your local comic book stores. Sometimes they have special editions or box sets available. Also, check the official publisher's website for direct purchase options.
Well, you could try looking at specialized manga retailers' websites. Some well-known ones include Right Stuf Anime and Book Depository. They often have a wide range of manga box sets available. Also, check out conventions or comic book fairs; sometimes vendors there sell such items.