Mix-mode or hybrid ventilation systems have been previously shown to reduce cooling and ventilation energy consumption. This paper presents a case study of a new ten story 83,700 ft² (7,780 m²) office building in downtown Tokyo with a hybrid ventilation system that uses only 1.7% of the building footprint for ventilation shafts. The control system design is presented as an example of balancing the comfort expectations of multiple tenants in a mix-mode system. On-site measurements are presented from a three week commissioning project to show: modest temperature differences within the occupied zone with a maximum difference of 1.5 °F (0.83 °C), large differences of up to 6.1 °F (3.4 °C) between the measured outdoor temperature in the control system and the actual inlet temperature for the natural ventilation system, the importance of smooth intergration of various design teams, and the use of low-power fans, 1.2-0.60 hp (900-450 W), that leverage the low pressure drop through the building when the naural driving forces are insufficient for pure natural ventilation. Practical lessons learned from the design and commissioning of the building are also shared.