No coming back
Remilia Scarlet had approved of Reimu and Marisa staying in a room at the Scarlet Devil Mansion. Patchouli Knowledge had not, but she was merely the librarian. She shut herself up in the library when the couple arrived. She'd always had a soft spot for Alice, Marisa knew. It was hypocritical, but she was still happy that Patchouli had never gotten anywhere with it. But if Marisa wanted to keep her situation with Alice alive, it was time to go back to her cottage, then set out to keep Alice company for a while. Reimu didn't enjoy being on the other side of the triangle, but she would put up with it. Marisa had been spending much more time with Reimu than with Alice, for a long time in fact.
She'd traded two rare books - one from Patchouli, in fact, and one from Alice, for special cuttings with which she'd grown spy plants near Alice's cottage. They were twin cuttings from the same psychic tree, and not only did they react to auras, health, and mental states of the beings near them, but what one perceived would affect their twin in another place. Alice had probably figured that out, right away, but left them alone, as it worked both ways: just by looking at the plants she could tell if Marisa was alive and well, and even when she was probably planning to visit. It took a bit of Green and Yellow magic gleaned from Alice to interpret them, but Marisa considered it effort well-spent. She could see Alice was anxious and lonely. Marisa tried not to feel bad; her motto was either don't do something or enjoy it.
Marisa was just about to straighten up when she remembered that Reimu had wanted her help with a magical ceremony this very night. She hadn't reminded Marisa when they parted, so it was probably partly a test. Too bad for her plans with Alice, but Marisa had to follow through. She grabbed a few magical necessities and headed off to the shrine.
Alice dragged herself out behind her cottage and sat down heavily. She wasn't really healed, but she could function. To test herself, still sitting down, she practiced seven hues of danmaku, at all nine of her levels. She started with the most strenuous, to see how she was doing, and amazingly, made it all the way through. A bit of rest and leaning heavily on her Tome should see her through whatever was going on. In her weary state, Alice's Divination senses were actually more acute. The one skill she was strong at was sensing phantoms, and out of the corner of her eye she saw a flock of them. They looked like the shades of the abandoned children on the Nameless Hill. Which ... meant Medicine had passed by her cottage without stopping. But this many shades clinging to her was unprecedented. In fact it seemed there were so many they were falling off and being left behind where Medicine had passed. Maybe her daughter was the Incident. She had a sinking feeling that was the case. She still needed to rest, but as she did so, she planned out how she could subdue and control Medicine without undue harm. It would be a challenge, if the number of phantoms she'd acquired was any indication. She opened the Tome and began reading, in chapters she hadn't considered since the Incident before last. A rough plan started to coalesce in her thoughts.
By this point, Medicine was an unstoppable ball of anger and hatred and disease and corrosion and death. She felt like a multitude in her cloud of poison. The crying of the children added to the pain in her heart, and it produced a beautiful and deadly harmony. Out of foolish sentiment she'd stopped by to peer at Alice, hidden by the shades. Her mother seemed to be injured slightly, and normally Medicine would have stayed and spied on her because of that. Especially this night, when it would probably be her last glimpse of Alice for years, until she visited Makai, at least. But she couldn't afford that. She decided to see Alice's condition as a lucky omen: at least she wouldn't be interfering tonight, so only Marisa had to be accounted for. She quickly made her way to the Hakurei shrine, where Hakurei Reimu was nowhere to be found. Using up some of her power, she traced Reimu to the Hakurei Barrier. The human shrine maiden was probably gathering supplies of some sort from the non-magical world. Medicine decided she could maintain herself and project her power for the few minutes it would take to destroy Reimu once and for all, so she went through the barrier. And she didn't sense any sign of Marisa. Perhaps the faithless witch was even now "comforting" the wounded Alice. Well, Medicine wouldn't care about any of that in Makai - and besides, killing Reimu would be adequate revenge if she read the black-and-white correctly.
Not a particularly sensitive magician, Marisa was suddenly anxious. It was probably an Incident if even she could sense something deadly ahead. Fortunately, she was more prepared than she'd ever been in her life. Marisa's secret was that Master Spark wasn't difficult to cast: in fact you didn't cast it at all. What was difficult was not casting it. As she'd developed it, based on information gleaned from a dozen stolen tomes, she crushed a ball of black and a ball of white energy together, wrapped it in a ball of red magic, then used her magical aura to crush it into a sphere the size of a pea. The black and white energies pushed each other away - the red magic of unmaking pulled them away - and nothing but her aura kept that energy compressed. The compression came as a steady flow of energy from Marisa's magical core. Releasing Master Spark actually enabled her to produce more danmaku, not less. That's why Master Spark always seemed to come out of nowhere when Marisa was fatigued and weakened. It was the holding back of the spell that exhausted and weakened her! But before she'd started taking up with Reimu, she'd had Alice show her how to make a ball of six different magics. Wrapping that in red magic took much more energy, and she'd had to develop a way to keep the energy looping in on itself without draining her. Really, it was one of the greatest accomplishments in Gensokyo history. She had bragging rights for the next decade, at least! She had prepared a seven-colored ball for protection during the ceremony. She'd probably have to use it for the Incident, instead. She had already been heading to the shrine, and now that, she realized, was where her anxiety was coming from. But when she got there, no one was around. Worse, inside the shrine something had blasted through, scattering the contents and Reimu's few belongings. The trail of chaos led to the Barrier. Marisa was human, but things like her Master Spark would only last a few minutes on the other side of the barrier. Nonetheless, she flew through without hesitating.
Alice was following Medicine's phantom trail, when suddenly the phantoms stopped moving, and all sense of Medicine vanished. As if she'd left Gensokyo. She wouldn't have had time to reach Makai, so logic dictated that she'd gone through the barrier at Hakurei Shrine. She quickly tried to sense Reimu - and of course, she could not. She used some strength she'd been trying to husband to lift herself in the air and move swiftly toward the shrine. When she cast her senses ahead, she could feel Marisa for a short while - then she disappeared, as well. Alice was starting to despair, a little.
Hakurei Reimu was maintaining, with some difficulty, a barrier to hide and protect her from animals and non-magical humans, but magically, she was completely unprotected, and facing away from the barrier, when Medicine came through. A stream of green vapor, pulsing with energy, shot out of the cloud Medicine was traveling in, and knocked Reimu forward at the same time as it choked off her air. The poisonous, life-draining, corrosive miasma started to settle on her, and she was losing consciousness. At that point, the Medicine ball was blasted - by her creator Alice's seven-colored energy, and by the energy of Marisa that had given her life to begin with. Medicine felt herself and her phantom children being shredded, but she didn't even turn around. The quicker she made sure that Reimu was dead, the quicker she could stun Marisa and escape. This didn't have to be a failure, and Marisa didn't have to be a casualty. She was not a weakling in any sense of the word, and her resolve was inhuman. More death energy poured out of her even as her own life force was crushed and her body was dissolving.
Marisa would never forgive herself if her affair with Reimu led to the girl's death. But, freed of the Master Spark weight, her magic rebounded, and she fired danmaku at a steady rate, right into the ball of green phantoms surrounding the presence she realized was Medicine Melancholy. She had no time to wonder where all that power had been acquired, making the doll girl a first class youkai. She dug in her heels and increased her rate of fire. She knew she could kill the doll-girl, and even the fact that Alice would never forgive her didn't make her hesitate; but she realized Reimu would probably perish, too. She saw black and green energy heading slowly towards Reimu, turning the ground to mineral and ashes as it moved forward. Marisa's shielding spells were never great, and especially on this side of the barrier. Then again, Medicine was, of course, weakening at the same rate or greater. Marisa acted quickly and flew in front of Reimu to confront the ball of Death. She threw up her shields, but the death energy flowed on, over the shield and tearing it slowly apart. And Medicine had one last trick, as she moved forward herself to envelop her victim in the ball of tortured, despairing children from the Nameless Hill. As they were human children (mostly) their phantoms actually lasted a longer time on the nonmagical side of the barrier. They were the only reason Medicine was still standing, and Marisa was pretty sure she, herselfwouldn't be, soon.
A ninth-level stream of seven hues of danmaku interrupted Medicine's journey toward Reimu. Then Alice swept through the barrier suddenly like an angel of light. The Tome was opened, and a white magic poured out of it as Alice recited an incantation in a language that was old even among the magicians of Gensokyo or the vampires of the Scarlet Devil Mansion. It was mixed with a red mist coming out of Alice's heart. In an instant, she was between Medicine and Marisa and Reimu. Marisa stopped firing, and Medicine stopped moving, but the miasma of death energy moved forward. When it reached Alice there was a blinding flash. The death energy was gone, absorbed by the white and blood magic barrier. Alice's eyes met Medicine's, as the last of the phantom children vanished. But the very last thing Alice saw was as her face turned and she met Marisa's eyes. While Alice's eyes were filled with profound sorrow, nonetheless - Alice smiled. Then Marisa saw the light go out of those eyes. Suddenly they were the blank, empty, lifeless eyes of what Alice was at her core, a doll. A doll made in Makai, that couldn't be alive in the nonmagical world. Her broken figure fell to the ground like a marionette with its strings cut, devoid of motion or a living aura.
Faced with the evidence of her mother's love for Marisa, and the forgiveness of her daughter that Medicine saw in Alice's dying eyes, the hatred that had been the only thing left animating Medicine ceased. She collapsed, much like her mother. Marisa was just pondering if she had the magical energy left to make sure Medicine wouldn't rise up and kill them both, when she heard a commotion from the other side of the barrier. Armed with tiny copies of Alice's Tome, Hourai and Shanghai, youkai in their own right, came out of the barrier. Shanghai picked up Alice tenderly and dragged her through the barrier. Hourai did the same thing for her eldest sister. As she did so, she looked back at Marisa and Reimu, and shook her head. They saw that two Goliath dolls were waiting on the other side of the barrier, and they picked up the bodies of Alice and Medicine once they were through it. Then Shanghai, Hourai, and the two Goliaths turned and silently departed.