みかみりあ.cpp

#include <memory>

struct Human { std::shared_ptr<Human> lover; };

struct Mika : public Human {};

struct Miria : public Human {};

int main() {
  auto mika = std::make_shared<Mika>();
  auto miria = std::make_shared<Miria>();

  /* 永遠の愛 */
  mika->lover = miria;
  miria->lover = mika;

  return 0;
}