Love Hina has more characters now, but somehow everything is exactly the same as it was in volumes 2-8. Serials are like that, so it goes.

Characters not mentioned above, segnificant or otherwise:

Grandmother - Keitaro's Grandmother is rarely mentioned, but it is hinted that she is a force to be reckoned with

Seta - Naru's previous crush, a flaky proffessor of archaeology who is often involved in Indiana Jones style adventures, although these are never explored in detail. Keitaro occasionally works as an assistant to Seta

Sarah - The youngest member of the Hinata family, Sarah is a rambunctious child who constantly breaks Keitaro's earthenware. Seta was her guardian, but decided that it was better if she lived in one place, since he traveled so much, so now she lives at Hinata House

Haruka - Keitaro's aunt, Haruka used to be Seta's assistant. Nothing seems to surprise her.
Mutsumi - An often sickly and accident prone student who ends up studying with Keitaro and Naru. Also a third year Ronin

Tama-Chan - A flying hot springs turtle, Tama-chan was a gift from Mutsumi. Su often engages in battle with Tama-chan, hoping ultimately to eat her. Strangely, Tama-chan is more popular than Su.

Gidget - A giant turtle which falls in love with Tama-chan on Pararakelse Island

Mecha Tama-chan (I, II, and III) - Su builds three Mecha Tama-chans as part of the ongoing battle between them.

Mecha Tamago IV - Su builds Mecha Tamago in order to aid in crossing the Desert of Death to save Keitaro and Naru

Krishna-chan - A robot built (by Su, of course) to help Shinobu learn how to kiss.