  We report the discovery of a multi-planet system orbiting HD 106315, a
rapidly rotating mid F-type star, using data from the K2 mission. HD 106315
hosts a $2.51\pm0.12\,R_\oplus$ sub-Neptune in a 9.5 day orbit, and a
$4.31_{-0.27}^{+0.24}\,R_\oplus$ super-Neptune in a 21 day orbit. The projected
rotational velocity of HD 106315 (12.9 km s$^{-1}$) likely precludes precise
measurements of the planets' masses, but could enable a measurement of the
sky-projected spin-orbit obliquity for the outer planet via Doppler tomography.
The eccentricities of both planets were constrained to be consistent with 0,
following a global modeling of the system that includes a Gaia distance and
dynamical arguments. The HD 106315 system is one of few multi-planet systems
hosting a Neptune-sized planet for which orbital obliquity measurements are
possible, making it an excellent test-case for formation mechanisms of
warm-Neptunian systems. The brightness of the host star also makes HD 106315 c
a candidate for future transmission spectroscopic follow-up studies.
