I'd suggest checking out local comic conventions or fan events. Vendors at those places sometimes have rare or hard-to-find manga box sets like the Hajime no Ippo one in English. Another option could be reaching out to manga fan forums or groups to see if anyone has leads on where to find it.
You might try looking on major online bookstores like Amazon. They often have a wide range of manga box sets available, including Fire Force in English.
Specialty manga stores or comic bookshops could be a good place to start. Sometimes they have rare or specific box sets like the one you're looking for. You can also check their websites if they have an online presence. Additionally, some conventions or comic expos might have vendors selling such items.
Yes, there's a big difference. The hentai version is usually adult-oriented and doesn't represent the true essence and story of the original Haikyuu manga.
I have no definite answer. Sometimes manga series end when the story feels complete to the creator or when publishing circumstances change. So, we'll just have to wait and see.
The Haikyuu manga is indeed over. It had a great run and left a lasting impression on readers. The story came to a satisfying end, tying up loose ends and giving closure to the characters' arcs.