Monster Hunter Stories

The game starts with the main character, whose gender can be selected by the player, and their friends, Cheval and Lilia, looking for a monster egg. They find a nest with one, which hatches into a Rathalos that bonds with the protagonist immediately. They nickname the creature Ratha. Upon their return to Hakum Village, a Nargacuga afflicted with a sickness called the Black Blight attacks. Ratha tries to defend the village, but is seemingly killed. Cheval's mother dies in the attack.
A year later, the village has recovered, but the threat of the Black Blight still remains. The main character takes the Rite of Kinship and is gifted by the village chief with a piece of Kinship Ore, a crystal with the power to tame wild monsters almost instantaneously. They then gain the title of Rider, which is unique to their village. They also meet a strange-looking wild felyne, who names himself Navirou and demands to accompany them. Traveling outside the village to tame monsters, they soon come across the Black Blight, which they are able to purify by using their Kinship Ore to resonate with a larger, natural formation of the mineral.
Lilia decides to join the Royal Scriveners, a group studying the Black Blight, while Cheval tames a Rathian and becomes fixated on slaying blighted monsters to get his revenge. Meanwhile, the protagonist continues to purify the Blight. Eventually, they encounter a mad scientist, named Doctor Manelger, who is attempting to create artificial Kinship Ore and bend monsters to his will. The main character reunites with Ratha, who is revealed to have survived the attack and flies to Manelger's laboratory, rescuing many kidnapped felyne slaves, as well as the Numbers, felyne test subjects of which Navirou was formerly a member.
To stop the Black Blight, the protagonist decides to look for the egg of a legendary white dragon, Versa Pietru that was once tamed by the very first rider, Redan. They find the egg, but it is stolen by Manelger. Manelger gives the egg to Cheval, who is wielding the artificial ore and the creature hatches and immediately grows to an enormous size. Cheval loses control of the creature which becomes infected with the Black Blight, turning into Makili Pietru. Cheval finally realizes his foolishness, and the protagonist rushes to defeat Makili Pietru before it can infect the entire world. Ratha's Blight, transmitted from a wound inflicted by the Nargacuga that attacked the village a year back, suddenly manifests and the player must defeat Ratha first. After Ratha comes to his senses, they face off against Makili Pietru.
After a long battle, the player and Ratha use Sky-High-Dive to try to finish off the Makili Pietru. During this time, Ratha is engulfed in a bright white light and empowered by Navirou to defeat the Makili Pietru, revealing that Ratha was actually the White Dragon all along.