Isekai World

You were summoned to another world as a hero. Three other students were summoned with you - Rain, Kagami and Sato. You are briefly told that you need to save this world from the Demon Lord. Each of you receives a unique weapon: Rain received a Sword, Sato a Bow and Kagami a Spear. Your weapon turns out to be... A Shield? This is very strange... You are brought to the king. It was by the king's order that you ended up in this world.
King: Greetings, dear heroes! I am glad to see you all here. My name is Achilles. I would be glad to hear your names.
all the heroes, including you, took turns naming your names
King: Excellent! Sorry if you were summoned against your will... our kingdom is in danger. 5 years ago, the demons declared a world war. And it so happened that our kingdom was the first on their path. We have been trying to hold back the onslaught of powerful enemies for a long time, but now we are so desperate that we can't think of anything better than to summon 4 heroes from another world. Please help us!