  Mrk 1388 has an unusual Seyfert nucleus that shows narrow emission-line
components without broad ones, but shows a strong featureless continuum and
strong iron-forbidden high-ionization emission lines. The apparent coexistence
of type-1/2 characteristics is potentially attributed to a heavily obscured
broad-line region or to an intermediate-mass black hole with a broad-line
component intrinsically narrower than those of typical narrow-line Seyfert 1
(NLS1) galaxies. Our observation using very-long-baseline interferometry (VLBI)
reveals high-brightness radio emission from nonthermal jets from an active
galactic nucleus (AGN) with a significant radio luminosity. Furthermore, we
investigate the radial profile of the host galaxy using a Hubble Space
Telescope (HST) image, which shows a Sersic index suggestive of a pseudobulge.
Using the VLBI and HST results, which are essentially not affected by dust
extinction, three individual methods provide similar estimates for the black
hole mass: (0.76--5.4)x10^6 M_sun, 1.5x10^6 M_sun, and 4.1x10^6 M_sun. These
masses are in a range that is preferential for typical NLS1 galaxies rather
than for intermediate-mass black holes. Based on the estimated masses, the full
width at half maximum $FWHM(H_\beta)$ of approximately 1200--1700 km/s should
have been seen. The scenario of a heavily absorbed NLS1 nucleus can explain the
peculiarities previously observed.

Astrophysics of Galaxies;High Energy Astrophysical Phenomena