Provided is a technology for a terminal apparatus, a base station apparatus, a method, and an integrated circuit which enable efficient communication with reduced complexity of protocol processing. A processing unit is included, the processing unit being configured to, in a case that release of an E-UTRA secondary cell group in MR-DC is triggered from NR, for an RLC bearer of a secondary cell group configured by the terminal apparatus, re-establish an RLC entity, release an RLC entity, and release a logical channel.