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Ren was a high school student before he he failed to save his childhood friend in his old world and was instead killed in the process of her rescue. Ren initially mistook the world he was summoned to to be exactly like the VRMMO game from his world "Brave Star Online" where Level came first and Status Boosts second in priority making his strengthening method extremely inefficient also leading to the collapse of his party. He acts like cool loner but he really does care for his comrades. However, he doesn't get close to them because he is terrible at team play. He carelessly killed a dragon which caused a plague as well as other problems. He is the youngest hero initially at 16, however after Medea kills him and he is banished to another world as a result, he spends two years there and becomes the second youngest at 18, according to Naofumi his appearance also becomes more rugged than before.
Ren is a person who acts cool and tries very hard to portray a loner's image. He runs his party like a guild, only working with the other members when the prey he seeks to kill is too strong for him alone. His particular attitude to this is that weaker members should work to individually increase their powers to catch up to the stronger ones.
Like the other heroes, Naofumi excluded, he is initially under the impression that the world they've come into is a game, and he stubbornly refuses to think otherwise. Unlike Motoyasu and Itsuki, Ren also seems to actually recognise to some extent the consequences of his actions, as he understood it was his fault the Zombie Dragon caused a plague. He is also more reasonable than Itsuki or Motoyasu, as he believed in the possibility that Naofumi was telling the truth when he claimed that Princess Melty was under his protection and not his hostage, and gave a proposal to help resolve the situation peacefully. He, alongside Itsuki, also stood up for Naofumi after Malty and Motoyasu tried to take Raphtalia from him via cheating, and called Motoyasu out for believing Raphtalia was brainwashed even when they saw her comforting an obviously crying Naofumi.
After his party was slaughtered by his, Itsuki and Motoyasu's, act of releasing the Spirit Turtle, his personality ends up taking a significant blow. His confidence has noticeably declined, and he has begun to realise that the world isn't a game and that his comrades are in fact dead and not coming back. To escape his guilt over this, Ren tries to blame them, stating they were too weak and got killed, something Naofumi and Eclaire both believe is a sign of his selfishness. He breaks further when Naofumi calls him out on this and also blocks his attack, he winds up calling it a cheat that the Shield is so powerful and runs off in anger. Later, due to his distraught state, he was easily manipulated by Malty, who gave him false words of comfort that he desperately needed to here. He ended up stripped of his belongings by her, abandoned and finally snapped completely, succombing to the Curses of Greed and later Gluttony.
While possessed by greed, Ren becomes a bandit leader and organises them to amass wealth, he also defeats people on the road and steals their stuff, but fortunately doesn't kill them. He becomes obsessed with increasing his power. After succombing to Gluttony this gets much worse, and he is willing to kill people to absorb EXP from them and grow stronger. His obsession with power is however either hollow or just an attempt to escape from reality, as when asked the reason for it he can only express the purpose given to him by others: saving the world. When he is finally defeated, he reverts to a broken, but otherwise normal, Ren.After being freed from his curses, Ren decides to learn under Eclair and try to save the world his late comrades loved so much. He also becomes steadily more open, though he is still rather timid compared to before and no longer puts up any elements of false confidence or a cool facade, he even notes outright that he wants to get to know the other heroes and get along with them from now on. He is no longer obsessed with power, and diligently began studying under Naofumi to learn the world's language. He has also resolved to help out the village any way he can and asked Naofumi to be given a job there. Finally, he has expressed regret over his past actions, especially when learning that the dragon he killed was acting as an adoptive father to one of the girls in Naofumi's village, Wyndia, who became a slave as a result of said dragon's death. After apologizing to Wyndia, and being slapped and told off for his trouble, he has began to interact with her roughly as frequently as Eclair, and is implied to have feelings for both of them.
After he joined Naofumi Ren more or less became the most motivated out of the heroes, and is the one Naofumi appears to get along best with, considering Motoyasu is now broken and insane while Itsuki is broken and emotionless. He acts with enthusiasm towards saving the world and repaying his debts to his former comrades in doing so, as well as repaying Naofumi. Finally, while he himself was enraged enough when Atla was murdered to awaken a Wrath Series weapon, he managed to talk Naofumi into calming down instead of pursuing his own perfectly justified anger.
Following his initial defeat at Medea's hands Ren spends two years in a different world training in the hopes of returning one day, his wish is granted when Naofumi, who underwent an even more massive "time skip" and became a god inside the void, appears and takes him back. Although he is somewhat upset that his two years of effort which turned him into a master swordsman proved minor compared to Naofumi's eons of effort that made him a god, he nonetheless chooses to retain them because the current him is more powerful than the former one. He also shows a completely new level of faith in Naofumi when he is told that it's safe to just lower his guard and attack the enemy without considering defence(because Naofumi used a skill to ensure all damage is transferred from his comrades to himself) and leaps into the battle without hesitation.
He is now also much bolder, proposing, albeit with the aid of alcohol, to both Eclaire and Windia during the celebration after the waves, the former of whom is much less stern in the face of his now more mature appearance(dropping the Japanese terminology for a moment, he basically is said to go from being a pretty boy to a manly man). much later, with Naofumi's subtle help, he even manages to marry both of them.
He partners up with Gaelion, Windia and Eclair most frequently.
Ren has a black hair with pretty handsome face and being described by Naofumi to be really suited as a protagonist of dimensional-cross stories from manga or anime bishounen. Later after two years time-gap when Naofumi's pick him from his world, he grew up to be more taller and has sturdy body due a result of a never miss training every day. He also has a mature-handsome appearance which perfectly labeled as an biseinen.
Ren specializes in water and support magic. There are some water spells that can heal.
Legendary Sword Skills
- 「Meteor Sword (流星剣)」
- 「Hundred Sword」
- 「Flashing Sword」
- 「Transfer Sword」
- 「Assassin Sword」
- 「Hide Sword」 
- 「Rakshasa Meteor Sword」
- 「Chain Bind」
- 「Chain Needle (Poison)」
- 「Gravity Blade」
- 「Flame Edge, Meteor Sword X」
- 「Instant Dragon Slaying」
- 「Gravity Sword」
- 「Soul Steal」
- 「Phoenix Gale Sword」
Curse Series Skills
Redo of Spear Hero
Loop 1 to 3 - Tutorial Arc c410-414
Loop 4 - Silt Welt Arc c415-455
Loop 5 - Melromarc Arc c456-574
Loop 6 - Foburei Arc c575-current