If Reimu is an antivirus program, and she attacks youkai, that means youkai must be viruses. Yukari is a youkai, so that means Reimu would have to eliminate her, causing the end of Gensokyo which would also destroy Reimu herself. Meanwhile, master hacker princess Kotohime laughs as her plan unfolds. That's what they get for dropping PC-98.
What if Sukuna enlarged Reimu's shrine?