Oh ABSOLUTELY NOT! Just take your time, man! Relax, enjoy the ladies, grind, do the Side Quests, Shambala, tear off ALL of the heroes' clothes (YES, you can collect those aka images of their clothes torn mid battle, just defeat them with a special attack!) You have all the time in the world, literally!
This is a SIDE STORY game and not a sequel! It has more characters than the original and a different story than the original. Basically, you can DIVE in this game without playing the first Eiyuu Senki! However, if you want to compare the stories, play them both for more in-depth lore.
PS: People really need to read my posts!