The Atacama Large Millimeter/submillemieter Array (ALMA) is now revolutionizing every
aspect of astronomy. In this talk, I will show our recent works on cold ISM properties
around active galactic nuclei (= AGN) near (z ~ 0; Seyfert galaxies) and far (z ~ 6;
quasars).

In nearby spatially resolvable Seyfert galaxies, we revealed that a 10-100 pc scale
cold, dense molecular gas disk is a direct source of fuel for mass accretion onto the
central supermassive black hole. The balance of nuclear mass flows therein is well
reproduced by a supernova-driven turbulent accretion model. Zooming-up to the center, we
have been investigating physical/dynamical structures of the so-called ¡Èmolecular
torus¡É. Our investigation toward the low-luminosity AGN of NGC 1097, along with other
studies toward more luminous AGN NGC 1068, suggest that a torus is not a steady but a
highly dynamic and evolving structure, depending on the central AGN¡Çs power and/or a
level of the circumnuclear star formation.

Regarding high-redshift objects, I will introduce our on-going ALMA follow-up
observations toward z >~ 6 quasars discovered by the HyperSuprime-Cam (HSC) on the
Subaru telescope. These quasars are characterised by their ~a few mag lower AGN
luminosity than previously known quasars at those redshifts. Based on [CII] and rest-FIR
continuum measurements, we found that the HSC-quasars show LIRG (luminous infrared
galaxy)-like star-forming nature, i.e., order(s) of magnitude less-active star formation
than most of the other highest-z quasars. Interestingly, these HSC-quasars already
exhibit a consistent M_BH vs M_host relationship with the local co-evolutionary
relationship, even at z ~ 6. Significant AGN feedback might had played a role in the
earliest universe to regulate the relationship.