  A radial velocity (RV) survey for intermediate-mass giants has been operated
for over a decade at Okayama Astrophysical Observatory (OAO). The OAO survey
has revealed that some giants show long-term linear RV accelerations (RV
trends), indicating the presence of outer companions. Direct imaging
observations can help clarify what objects generate these RV trends. We present
the results of high-contrast imaging observations or six intermediate-mass
giants with long-term RV trends using the Subaru Telescope and HiCIAO camera.
We detected co-moving companions to $\gamma$ Hya B ($0.61^{+0.12}_{-0.14}
M_\odot$), HD 5608 B ($0.10 \pm 0.01 M_\odot$), and HD 109272 B ($0.28 \pm 0.06
M_\odot$). For the remaining targets($\iota$ Dra, 18 Del, and HD 14067) we
exclude companions more massive than 30-60 $M_\mathrm{Jup}$ at projected
separations of 1arcsec-7arcsec. We examine whether these directly imaged
companions or unidentified long-period companions can account for the RV trends
observed around the six giants. We find that the Kozai mechanism can explain
the high eccentricity of the inner planets $\iota$ Dra b, HD 5608 b, and HD
14067 b.
