権利関係
共有の間違えやすいポイント
保存・管理・変更の要件
保存行為＝単独可／管理＝持分価格の過半数／重大な変更＝全員の同意。不法登記の抹消請求は保存行為として単独可。
持分の放棄は他の共有者へ
放棄・相続人なき死亡の持分は他の共有者に帰属。「国庫に帰属」はひっかけ。
単独占有者に当然には明渡し請求できない
共有者の一人が勝手に単独使用していても、その者にも持分権があるため当然には明渡しを求められない。
分割請求は原則いつでも自由
ただし5年以内の不分割特約は有効（更新も5年まで）。
遺産分割前でも共有物分割訴訟可
共有者の一人が死亡して共同相続が生じても、他の共有者は相続人らに共有物分割の訴えを提起できる。
賃貸借の解除は過半数でできる
共有物の賃貸借契約の解除は「管理行為」として持分価格の過半数で可能（544条の解除不可分の例外）。
English: Co-ownership
Preserve alone / manage by majority / alter unanimously
Preservation acts: any co-owner alone. Management: majority by share value. Major alteration: all consent. Removing a stranger's false registration = preservation.
Abandoned share goes to co-owners
On abandonment or death without heirs the share accrues to the other co-owners — NOT the treasury.
No automatic eviction of a sole-occupying co-owner
Even an unauthorized occupant co-owner has a share-based right, so others can't simply demand the whole property back.
Partition on demand
Any co-owner may demand partition anytime; a no-partition pact is valid up to 5 years (renewable).
Partition suit OK before estate division
When a co-owner dies, remaining co-owners may sue the heirs for partition even before the estate is divided.
Majority can terminate a lease
Terminating a lease of the common property is a management act — majority by share value suffices.