She first appears in chapter 1, when Ogretooth attempts to attack a young boy in Lady's Village. The oni jumps in to defend him and prepare to fight the three succubi, even if she's reluctant to intervene as she feels too old for this. She then presents herself to the duo of Lauratt and Rigeo as the elder of the Mahoroba Mountain of Yamato. When the latter tells them they never heard about it, she answers that she doesn't know about their town Lendeica or the Witch of Order they talk about. She asks the duo if they've seen her disciple, Hakunen but is met with a negative answer.
She compliments Lauratt's skills, telling him that his master must be proud. She's as surprised as Rigeo and Lauratt when the White Rabbit shows up and tells them that she will guide them.
In chapter 5, the party decides to go to to Succubus Village in hope of getting some information and support. They meet Succubus, and after Rigeo informs them of their nature, she calls Witch and have her help Lauratt grow her skills in magic.
While Lauratt trains, Magatsu busies herself by drinking and thinking about Hakunen while helping the mayor harvest potatoes.
Once his training is over, Witch tells that Lauratt should contract with the Four Spirits, and Salamander is relatively close so he should start with her. The whole group then decides that Lauratt should indeed get to make a pact with Salamander in Gold Volcano. Should the party attempts to enter Gold Port, she will remark that the town is known to be hostile to monsters and should be avoided.
After Lauratt forms a contract with the Fire Spirit, Fulbeua appears and exposes her plan to bring the "Château des Romances". Magatsu is dumbfounded by the narcissistic attitude of the succubus. None the less, the party can't ignore the looming threat as well as the emergency of the situation, and decides to rush to Grand Noah.
Her party shows up again in chapter 6 to save Kazuya's group from Myusca, Vinum and Nemea. They then introduce each other, and focus toward Grand Noah. She's glad to see that Hakunen is safe, and embarrasses him in front of Kazuya.
The party is aghast at the realization that they're too late to prevent the summoning of the Château des Romances. Even then, the group frontally attacks the places with the goal to reach Fulbeua. When Rigeo remarks that the gargoyles aren't awake, cluing her in that the summoning is incomplete, Magatsu asks what they are as she never heard of gargoyles, before hearing that they're statues that cant turn their victims to stone.
They are blocked by a barrier that needs to be deactivated first. In the kitchen, they meet a nightmare who's ready to tell them where the switch in exchange for a little energy from one of the males. Afterward, the party comes face to face with Fulbeua herself, and attacks her in hope of getting information about the gate's location. However, Musette steps in and asks Fulbeua to deal with the intruders appropriately. As conflicts rise between the two of them, the party uses the opportunity to run away. The moment they think they managed to escape the throne room, Myusca, Nemea and Vinum appear to chase them, with Vinum teleporting later again to block the exit. The party is forced underground, and fights Vinum who is alone.
When they're surrounded by the three succubi, However, Luka and his companions arrive to save them. As the situation becomes more chaotic, the succubi negotiate their retreat.
She continues to accompany the party afterward when everybody introduce themselves. She's displeased by Daimyokai's presence, but none the less tolerates her, as she proves a valuable support.
She supports the assault on the Château des Romances, and is completely shocked by the appearance of the Apoptosis showing up at the entrance. When the party encounters Fulbeua again as everyone attacks the Château des Romances, Magatsu can't help but notice again how narcissistic the nightmare is.
When the party fights Est, she gets incapacitated just like everyone who's not one of the seven heroes.
Once everyone is back in the castle and it's clear that they can't come back to their worlds yet, Magatsu remarks that Daimyokai left them after the battle and should be found, as she remains a powerful yokai hunter and a threat at large.
In the post-collab, Magatsu intervenes several times. She's annoyed, but not surprised when Daimyokai shows up near the Snow Shrine to announce her intent to capture Musette and get the reward for herself. When the yokai hunter is beaten, Magatsu is reluctant to join force with her, but says that it's likely for the best as it's out of question to let her alone as she's too obstinate to do anything else but attempt to attack monsters again.
When the party sees Fulbeua yet again, Magatsu tries once again to be passive agressive, which utterly fails and make her feel like she's acting like a trained beast, even as Hakunen remarks that they seem to get along better.
When the party reaches Finoa again to clear the Succubus Prison Trio from the village, she is displeased by Nemea's attempts to hit on her apprentice. When they reach Myusca's first sex room, Hakunen gets hit on by Daimyokai, but Magatsu ends up taking the lead and have her way with her apprentice, saying that she enjoyed this break. When the party reaches the Karaoke Handjob challenge, Hakunen volunteers first and gets thoroughly embarassed, something that Magatsu enjoys a great deal. When the party reaches the sixth room, Magatsu wisely tells Hakunen to hold back as the latter attempts to mediate a conflict between Luka's companions. When the party is finally done and has beaten the succubus trio, Magatsu offers to protect Hakunen at night by sleeping with him.
Magatsu: “Hmm, all right. Gotta move my body once in a while.”
- SP +20% - Combat Ability
- Black Yamabiko - Taoism Skill (Dark 1400% ^ of Mag, Dex), Target: All Foes, Effect: Death (50%)
- Calamity Oni Blaze - Taoism Skill (Fire 1400% ^ of Mag, Dex), Target: All Foes
- Dragon-Gorged Flood - Taoism Skill (Water 1400% ^ of Mag, Dex), Target: All Foes
- Crashing Dragon Fang - Club, Critical Rate +15%, Critical Damage +100%
- Six Soul Banner - Clothes, Six Soul Banner Counter
- Oni's Sake Gourd - Max HP +30%, Attack +30%, Battle Start SP MAX, SP Regen +20%, Nullify Poison/Blind/Confusion/Sleep