I forgot what is called to the person who is helping a team in a match (example basketball,soccer and baseball)... Since Hayasui is seen as that.
In Japan, as shown here, the 'Manager' is the support-person for a team - usually in school club. Normally, the manager doesn't actually play, and it's often shown in manga as the position for someone to get closer to their romantic interest in the club. In real life, they might also do administrative duties and may assist with coaching, if only through providing encouragement.
Professional teams would have similarly professional, and more specialised support staff - viz. Waterboy, physio, cameraman and whatnot. Hence a 'Manager' would probably be an actual manager.
Also, I can prepare some beverages too!Yep.Ma...Manager?Don't you think?Hey, you two! How 'bout some onigiri?It's at times like this that you start to get hungry.
