Coupling system for fluid transfer

A coupling system (300) for fluid transfer and a system (500) for transferring fluid into a patient are provided. The coupling system comprises a first tube (340), at least one second tube (370), a coupling device (400) configured for connecting the at least one second tube with the first tube wherein the coupling device comprises at least one first connector element (410) and at least one second connector element (420), the at least one first connector element and the at least one second connector element are configured to be matingly connected to effect a connection between the at least one second tube and the first tube, where the first connector element comprises a first sealing element (430) and a tube portion (440), and where the second connector element comprises a second sealing element (450), whereby the first sealing element (430) and the tube portion (440) are sealed by the second sealing element (450). In the connected state of the coupling device, the tube partially protrudes through the first an