Jonatan Lejon is originally a character from The Brothers Lionhart by Astrid Lindgren. The visual of this character is taken from Vantomen, the Swedish version of The Phantom comic.

In the adaptation towards Masculine War, he is a gunsman deployed by the Howling Voice Guild to gain information of the Beast Rune's condition in Higheast's L'renouille castle. After he leaves for Higheast, his whereabouts is unknown. Howling Voice Guild brands him as a heretic and deploys his adoptive brother, Rusky Lejon to continue his job and capturing him at the same time.

Jonatan sneaks into L'renouille successfully but is unable to locate the Beast Rune, Instead, in the main hall of where the true rune is supposed to be, he finds a group of floating crystals. At this point of time the Higheast soldiers are aware of his presence and in panic, he destroys one of the crystal, granting him the Blue Beast Rune.

He manages to escape from L'renouille but only finding himself slowly turning into a beast. He decides not to return to Howling Voice Guild but searches for the answer of the mysterious rune he has just bore. He sets south east for Temasek. In the middle of Temasek is a small island called Toba, surrounded by a magnificent lake. He finds the ancient tree of knowledge, Yggdrasill underneath the island and resides in Långholmen temple.  

Rusky meets Jonatan, no longer in his recognizable Howling Voice Guild attire when Rusky is on board of Vassa, the great ship that sails from Berastagi to Toba. He is already known as the Vantomen, the 'creature' that brings bad omen to ships. Jonatan tries to communicate with Rusky but the ship sinks shortly after she takes her maiden sail.

Jonatan remains with the sunken Vassa, only later is discovered by Rusky to join the Masculine War. The brothers learn the truth of the reasons behind their runes which Jonatan learns during his refuge at Långholmen temple. 

He joins the war as Tensyo Star 天捷 also known as the Swift/Agile Star 天捷星. He takes over Clive, Yun, Travis and Haswar from gensoSuikoden and Zayin from Tierkreis. The original Shui Hu Zhuan 水滸傳, this star belongs to Zhāng Qīng, nicknamed Featherless Arrow 沒羽箭. This star is numbered 16th.

After the war, together with Hang Nadim the trio attacks Howling Voice Guild.