  We present spectroscopic and photometric observations of 17 dwarf-nova
superoutbursts obtained by KOOLS-IFU mounted on the 3.8 m telescope Seimei at
Okayama Observatory of Kyoto University and through VSNET collaboration. Our
spectroscopic observations for six outbursts were performed within 1 d from
their optical peak. 11 objects (TCP J00590972+3438357. ASASSN-19ado, TCP
J06073081-0101501, ZTF20aavnpug, ASASSN-19ady, MASTER OT J061642.05+435617.9,
TCP J20034647+1335125, ASASSN-20kv, ASASSN-20kw, MASTER OT J213908.79+161240.2,
and ASASSN-20mf) were previously unknown systems, and our observations enabled
quick classification of their transient type. These results illustrate that
Seimei telescope has the capability to conduct quick follow-up observations of
unknown transients. Our photometric observations yielded that 11 objects are WZ
Sge-type dwarf novae and their candidates, and the other six objects are SU
UMa-type dwarf novae and their candidates. The He II 4686\AA~ emission line was
clearly detected among ASASSN-19ado, TCP J06073081-0101501 and MASTER OT
J213908.79+161240.2, whose association with a spiral arm structure in an
accretion disk has been suggested in the previous studies. Our result suggests
that a higher-inclination system shows a stronger emission line of He II
4686\AA, as well as larger-amplitude early superhumps.
