|Appears in:||Digimon Cinematic Sagas|
|First appearance||Digimon: Ordeal of Deva [M7]|
|Last appearance||Digimon: Judgement Code [M9]|
|Digivice(s):||Blue and Grey D-Ark|
|Age|| 19 (Ordeal of Deva)|
20 (Evolution Beyond and Judgement Code)
Riku Arhinmäki is a fanfictional character in the Digimon Cinematic Sagas. He is the one of the secondary characters in the Legendary Tamers Saga.
Riku was born in 2004 to unrevealed parents. He has lived in Helsinki, Finland, and is skilled at card games, including the trading card game developed about the Digimon right after the Digitaclysm. Because of becoming the Champion of the game in his home country and participating in international tournaments as well, he is well known, but his parents aren't very happy about this. In 2022, he met the DigiGnomes who gave him a D-Ark and sent Cyberdramon, who is also his favorite card in the game, to become his Partner Digimon. Cyberdramon was a little bit violent and wanted to become part of the battles that were happening on the other parts of the world.
In 2023, when Riku had graduated from upper secondary school, DigiGnomes reappeared and guided Riku to go into the Digital World to find a way to properly tame Cyberdramon and help to defeat a new threat to the two worlds. Therefore, Riku decided to leave into the Digital World without having any courage to tell the truth to his relatives.
Riku makes a cameo appearance in the mid-credit scene where right after his arrival into the Digital World, he and Cyberdramon had crossed paths with Anilamon the Dragon Deva in the Desert Layer. Cyberdramon's fierce nature had forced to help fight it. Anilamon was defeated, but Cyberdramon was not satisfied, so Riku promised to help him find a worthy opponent.
One year later, Riku still had trouble to get Cyberdramon calm down. When they visited Jijimon and Babamon, they found out that Jason Storm, Kyle Lambert, Vera Neidhardt and Mei Yashida from New York had appeared into the Digital World too. Jason and Kyle knew about him and excited to finally meet him, but Vera disliked him. Riku heard everything about the Deva and Calumon, the source of all Digivolution. After that he told how he had defeated Anilamon and how he was now going to find a worthy battle for Cyberdramon to make him calm down. Until then he helped the Tamers to reunite with Tatsuya Munemori, Andrew "Andy" Conteh and Susan Conteh.
Riku and Cyberdramon found their way into a place where Cyberdramon wished to challenge Apollomon, a member of the Olympos XII. But Apollomon persuaded them to fight against a true enemy. After Cyberdramon expressed his desire to know about him and Apollomon sensed how the other Tamers had ended up into a conflict with Mercurimon, Riku joined them to end the fight. But it was only after the arrival Harold Thompson and Kudamon with a holographic apparition of Grigory Shatalov when everyone heard the truth. The enemy was D-Reaper, a malevolent multi-agent program who believes that humans and Digimon don't deserve to exist. When D-Reaper attempts its first attacks, it appears to be a powerful opponent even for Cyberdramon. When the Tamers return to New York, Riku and Monodramon (Rookie form of Cyberdramon) ask for another portal, one which would take him back to Finland.
Riku's father was very angry at him leaving his studies and not contacting his relatives. Riku had to apologize several times, but he refused retire as a Tamer and kept Monodramon with him at his new apartment he had been able to find. After he had unpacked his remaining stuff, he checked the news and found out how D-Reaper had started to invade Earth cities, including Helsinki. He decided to go defend his home with Monodramon who Digivolved back into Cyberbramon.
In North America, Edmund Harmon and Gia Avilés as well as their Partner Digimon Patamon and Tailmon restored the ability of each Partner Digimon to Digivolve into their Ultimate and Mega forms. They also gave the Tamers an ability to Biomerge with their Partner Digimon in the real world, allowing Riku to Biomerge with Cyberdramon into Justimon. Justimon traveled into the United States to help his friends to fight against D-Reaper.
After D-Reaper's main body where real Mei was kept as a prisoner were located in the Core Layer of the Digital World, Riku and Cyberdramon joined the final battle along with other Tamers, Apollomon, Mercurimon, Omegamon and Imperialdramon. During the battle, Justimon asked more power to defeat an ultimate ADR, simply called Reaper, and Sakuyamon gave much of her power for him to make his weapons more powerful. When Beelzemon is wounded and Grani damaged, and later, the effect of the Red Card that causes the Partner Digimon to Digivolve. Riku, however, witnessed how Tatsuya and Guilmon managed to use the data of the White Card to shut down D-Reaper. Riku, however, decided to become only as a reserve member of the United Digital Activity Agency in order to balance his personal life and make amends with his family.
- Riku is mostly based on Ryo Akiyama since he has Cyberdramon as his partner and he is a card game champion as well as having been in the Digital World long before other Tamers.
- Riku's nationality is partly inspired by Miska Saari, a Finnish Pokémon trading card game world champion from year 2006.
|Characters in Digimon Cinematic Sagas|
|DigiDestined:||Troy Dawkins & Agumon | Seamus Maitland & Gabumon | Jake Thacher & Betamon/Gomamon | Miyuki Koharuno & Piyomon | Kevin Harmon, Tentomon & Armadimon | Edmund Harmon & Patamon | Dan Linwood & Veemon | Wei Xueqi & Wormmon | Gia Avilés & Tailmon | Nadia Coetzee & Palmon | Omegamon | Imperialdramon|
|Digimon Tamers:||Tatsuya Munemori & Guilmon | Andy Conteh & Terriermon | Vera Neidhardt & Renamon | Harold Thompson & Kudamon | Mei Yashida & Wizarmon | Jason Storm & Hagurumon | Kyle Lambert & Piccolomon | Susan Conteh & Lopmon | Riku Arhinmäki & Cyberdramon|
|Other characters:||Robert Harmon | Calumon | Impmon | Grigory Shatalov | Huckmon|