Koichi is in fact, Koji's unknown brother. Koichi had found out about Koji from his dying grandmother. He found Koji and was closely watching him, until the day he decided to follow him. Koji was following the messege on his cell phone to the Digital World, with Koichi following behind, unknown to Koji. Koichi was running for the elevator Koji and Takuya were on, but missed it and began running down the stair's. He tripped and fell, landing on the floor below, muttering the name "K..Koji."

It seems Cherubimon took Koichi to the Digital World and with a corrupted Darkness Spirit, he Spirit Evolved Koichi to Duskmon. Duskmon is a Digimon with GODLY powers. He is excellently strong for a human hybrid, and his battling skills prove so. The only true rival Duskmon has is BeoWolfmon. Velgemon, Duskmon's Beast Spirit, is even more powerful then Duskmon, using more strengh from Cherubimon. Velgemon loved toying around with BeoWolfmon. It took the strengh of him and Aldamon to take Velgemon down, returning him to Koichi.

Once Koichi was free of Cherubimon's control, Koji's D-Tector cleansed the Spirits of darkness. They became Koichi's true or "Hero" Spirits of Darkness. He also received a grey and black D-Tector. Loewemon is the "true" human form of Koichi. Loewemon is fast and strong. He wields a dark staff and sheild of a sphinx's head. JagerLoewemon is fast also. He is an excellent jumper and when he gains enough speed, he can fly through the air at top speeds, allowing him to use one of his attacks. JagerLoewemon has strong, feirce nails to thrash through his opponents.

Koichi was thrilled when Koji acually accepted him as his brother. A lot of the battles against the Royal Knights, Koji saved Koichi, and Koichi couldn't believe he would acually save him after all the pain he brought to him. Whenever the DigiDestineds would get kocked out cold, their Fractal Code would appear.. Well, all of them except Koichi. Crusadermon informed Koichi that he didn't have a fractal code because he was only a spirit.

While fighting Lucemon Chaos Mode, Lucemon unleashed his ultimate attack against the group, Ultimate Sacrfice! The attack blends darkness and light together into a deadly combination. Loewemon placed himself between the darkness and light, making the attack avoid the group as he took the full blow! Lucemon Chaos Mode scanned Koichi's Fractal Mode, as the Spirits of Darkness were passed on to Koji.

After the DigiDestineds defeated Lucemon, they return home and race to the steps where Koichi had fallen. He wasn't there-- Koji busts through the doors at the local hospitle to find Koichi laying on a bed, almost colorless with the doctors saying it doesn't look good at all. Koji tears up, and everyone's D-Tector begins to glow. A tear falls from Koji's cheek onto Koichi's forehead, as color returns to his body.