  We present an investigation of spin-orbit angles for planetary system
candidates reported by Kepler. By combining the rotational period $P_s$
inferred from the flux variation due to starspots and the projected rotational
velocity $V\sin I_s$ and stellar radius obtained by a high resolution
spectroscopy, we attempt to estimate the inclination $I_s$ of the stellar spin
axis with respect to the line-of-sight. For transiting planetary systems, in
which planetary orbits are edge-on seen from us, the stellar inclination $I_s$
can be a useful indicator of a spin-orbit alignment/misalignment. We newly
conducted spectroscopic observations with Subaru/HDS for 15 KOI systems, whose
lightcurves show periodic flux variations. After detailed analyses of their
lightcurves and spectra, it turned out that some of them are binaries, or the
flux variations are too coherent to be caused by starspots, probably
representing ellipsoidal variations, and consequently we could constrain
stellar inclinations $I_s$ for eight systems. Among them, KOI-262 and 280 are
in good agreement with $I_s=90^\circ$ suggesting a spin-orbit alignment, while
at least one system, KOI-261, shows a possible spin-orbit misalignment. We also
obtain a small $I_s$ for KOI-1463, but the transiting companion seems to be a
star rather than a planet. The results for KOI-257, 269, 367, and 974 are
ambiguous, and can be explained with either misalignments or moderate
differential rotation. Since our method can be applied to any system having
starspots regardless of the planet size, future observations will allow for the
expansion of the parameter space in which the spin-orbit relations are
investigated.
