Now that Crono has the Dreamstone, with his other party members (Marle, Lucca, and/or Robo), they have to go to Melchior's Cabin, in Medina Village, in the Present. Melchior will help fix the Masamune. Melchior gets confused, because of how you got the Masamune and the Dreamstone. He doesn't think it matters, time to fix it. After the Masamune gets fixed, it's time to go back to the Cursed Woods in the Middle Ages. When they get to Frog's House, Frog gets shocked to see that the Masamune is whole. Frog needs to know it's power, he asks Crono, and the others to remain for the night.
Flashback: While Frog is doing stuff with the Masamune, it'll show a flashback of Sir Cyrus talking to King Guardia XXI, and Queen Leene about his travel to seek the Hero's Badge from the Frog King. The King and Queen with him, and Cyrus's friend Glenn safe travel. When Cyrus, and Glenn, are looking for the Frog King, they encounter some Nagas. When they find the Frog King, he will not lend the Badge to Cyrus. Then Cyrus strikes the Frog King, and the Frog King lets go of the Hero's Badge and flees. While Cyrus is fighting Magus, and Ozzie, in the Mountains. Cyrus loses his sword (the Masamune). Cyrus tells Glenn to flee. But Glenn refuses. When Cyrus begins to strike Magus, Magus shoots Lightning (or some other power) at Cyrus and Cyrus falls. Cyrus tells Glenn, very painfully, to take care of Queen Leene. Then Cyrus caught on fire and dies. Glenn gets mad, at the Fiend Masters. Then Ozzie asks Magus for a better form. Magus shoots a magical attack at Glenn, and he falls off the cliff.
Back at Frog's House, Frog is thinking about Cyrus, and the powers of the Masamune, then a tear drops out of Frog's eye, and lands of the Masamune. Frog wakes up Crono, and the group. Frog is ready to slay Magus. Onward to the Fiendlord's Keep. Now Frog joins your party. Give Frog the Hero's Badge, before you go.
Go to the Magic Cave, and it'll show another flashback.
Flashback: Glenn (as a kid), gets bullied by other kids, but Cyrus comes and saves Glenn. Cyrus tells Glenn, he should step up like a man, but Glenn doesn't want to, he hates hurting people. Another scene shows Cyrus at Zenan Bridge, telling Glenn he is joining the Soldiers against the Fiendlord. Cyrus asks Glenn to come with him, but Glenn still doesn't like killing people, even Fiends. Then the next scene comes back to Magus, and Ozzie, killing Cyrus, and Magus shoots a magical power at Glenn, and he falls off the cliff. Down the cliff, it shows Frog, and the Hero's Badge falling off the river.
Back with Frog, and Crono, and another player at Magic Cave, and Frog says his real name is Glenn, and he held Cyrus's hopes and dreams. Frog grabs the Masamune, shoots it at the air, then slashes the Magic Cave, and it opens. It shows it as a cutscene. Once the group gets inside the Magic Cave, kill some Grimlings, and Vampire Bats. Near the exit to Magic Cave, it'll show blood on the wall, saying "Beware the Jugglers, strike them, and they will tighten their defenses. Cast magic, they will tighten their magic defenses." Go outside Magic Cave, and see that you've made it to Magus's Castle.