Giant killing is one of the Mangas which cover almost all the aspects of a Football club from players to Mangment to fans. It has everything a sports manga should have and from my pov I rate it as the best sports manga ( above SD, Haikyuu) The author also had gone deep in J1 league Getting back story of Other teams and their players and mangers. There is 2-3 arcs solely about the Club Ultras (regular supporters) As a football enthusiastic I recommend this Manga to Every football fan and if you don't watch football Then this will give you a whole new experience about howa club and it's player work in sync for a club.

10/10 for me now It's Scalnation team dropped it at 514 The raws are in 630+(as of now) Kodansha USA is releasing it's vol from start In 2017 Bi monthly (Till 40 vols have come online) I am also waiting for new ones Tho I have to wait 2-3 yrs more But you should definitely check this out