Red Dragon Emperor - Master of the Grand Order

Issei Hyoudou a true hero who saved his world from the Beast of Apocalypse. One day he didn't went to the party to celebrate their victory against chaos brigade, and The beast of apocalypse because today was the day was win his grandfather died. He said his grandfather was a respectful man, who said to the young Issei "Does it frustrated you kid. Does it Upset you to be the weakest one? That's good, hold on to that feeling. It's proof that feeling means you are not yet ready to give up on yourself." Those words hit very deeply in Issei he didn't remember them until now when those memories flowed back to him when his grandpa spoke to him. After finishing giving the respects to the grandpa. Issei decided to go to the party but what he saw, broke his heart and made the leaders angry and sad for him reason why? It's because the Gremory group, including Kuroka, Le Fay, Yasaka were flirting and kissing random men. Everyone was thinking of punishing them, but Issei didn't want to instead he said " They got a swear that they don't regret the decision" so that day changed Issei who started to pursue his passion with sword including saving someone who became someone precious to him, and ones he loves named Ingvild Leviathan, Laita Astaroth, Elmenhile Karnstein Ophis. After finishing college, making his parents proud he decided to help the factions (Not known three of the most beautiful women of the factions were in love with him since he also save them). Reason why he was helping the factions was because he needed the money for a surprise for his beloved that being a Ring! But sadly things don't go as they planned because one day Azazel started a machine that would travel dimensions an accidental he sucked. What happens to our beloved hero? Why is the summoning heroes from the past? And how come he can't use all the power of the booster gear? And will he use his sword skills? And why is he together with a girl saving humanity?