In Rosario + VampireEdit
Issa Shuzen is seen as the head of the Shuzen Family. In the flashback into Moka's memories, he is shown to own a fairly large European-styled castle, which is the meeting place for vampires in all of Japan, and is apparently well known in the yōkai underworld for being the one to go to when a problem needs to be 'solved'. He also fits the general expectation of what one expects a vampire of his status to look and behave. When Akua is first introduced, he seems to be caring enough to make sure that Moka, Kahlua, and Kokoa all introduce themselves formally to Akua. However, right after that, he tells Kahlua and Akua to 'kill each other' without holding back.
Touhou Fuhai explains that the Shuzen house is probably the most fearsome place in all of Japan due to the high number of vampires who live there. Based on Akua's attack and subsequent deduction of Kahlua's tears, Issa stopped the match with a loud clap. The clap was with great strength, so strong that it chocked Kahlua and Akua in fear. It appears he determined the two's strength within a minute of battle. When he is warned of the possible threat of intruders, he merely brushes it aside, believing it to be yet another attempt to try to kill him. He states that if they managed to get into the castle, that he will take their challenge personally.
Despite his brutal nature, he treats his family rather well, celebrating his daughters' birthdays with them. He even seems supportive of Akasha's plan to have Moka leave the mansion for fear of having something happening to her because of 'that thing in the basement'.
In the most recent chapters, Issa is revealed to be the leader of Fairy Tale's 2nd Subdivision when Gyokuro says to Touhou Fuhai that his opponent was not her but rather behind him (refering to Issa).
he created Moka's Rosario Cross and the one used for the school barrier. His contempt for humans knows no bounds and, according to Koumori, his powers exceed that of a standard S-class yōkai, able to throw anyone with just a wave of his hand. Moka's father resided in a vast castle when Tsukune Aono went in search of him for another Rosario cross. Upon meeting him, he hated Tsukune because he chooses a "fake" Moka over his real daughter however he gains a begrudging respect for him once he takes the Rosario out of his hand without him knowing. As Inner Moka arrived and stopped the fight claiming that Tsukune would have lost if he kept fighting the way he was fighting (she claimed if he was truly fighting seriously, Tsukune would have lost instantly). With this, he lets Tsukune keep the Rosario and he leaves, causing the castle to collapse. Before leaving the area, he realizes that Kokoa Shuzen was behind the events which caused so many people to "bug him" so he gave her a big spanking for causing him so much trouble.