The multi-planet system TOI-421 -- A warm Neptune and a super puffy mini-Neptune transiting a G9 V star in a visual binary

KESPRINT collaboration, an international consortium devoted to the characterization and research of exoplanets discovered with space-based missions NASA's Science Mission directorate NASA High-End Computing (HEC) Program through the NASA Advanced Supercomputing (NAS) Division at Ames Research Center National Aeronautics & Space Administration (NASA) European Research Council (ERC) 817540 European Research Council under the European Union's Horizon 2020 research and innovation program 832428 CRT foundation 2018.2323 Comision Nacional de Investigacion Cientifica y Tecnologica (CONICYT) CONICYT FONDECYT 3180246 Millennium Science Initiative, Chilean Ministry of Economy IC120009 Comision Nacional de Investigacion Cientifica y Tecnologica (CONICYT) CONICYT FONDECYT 1171208 Irish Research Council for Science, Engineering and Technology GOIPD/2018/659 Swedish National Space Agency DNR 65/19 136/13 Australian Research Council 170100521 NASA through Caltech/JPL grant RSA-1006130 NASA through TESS Guest Investigator Program 80NSSC19K1727 Alfred P. Sloan Foundation National Aeronautics & Space Administration (NASA) 80NSSC18K1585 80NSSC19K0379 National Science Foundation (NSF) AST1717000 Spanish Government RYC-2015-17697 FPI-SO from the Spanish Ministry of Economy and Competitiveness (MINECO) SEV-2015-0548-17-2 BES-2017-082610 National Aeronautics & Space Administration (NASA) NNX17AF27G HeisingSimons foundation PLATO grant GOLF CNES grant CONICYT-PFCHA/Doctorado Nacional, Chile 21140646 German Research Foundation (DFG) PA525/18-1 PA525/19-1 PA525/20-1 HA3279/12-1 RA714/14-1 National Aeronautics & Space Administration (NASA)