Inserter and insertion system

Insert includes an insertion portion which is inserted into the lumen, is disposed in the insertion portion of the insertion portion to be inserted into the lumen, the tube insertion portion at a first position inside the lumen having a fixed portion fixed to the cavity, and a positioning portion that is disposed outside of the mounted by lumen against sites exposed to the outside of the lumen in the insertion section. Positioning unit positions the insert portion into the second position in the external lumen.