Kono kanji wa kakijun ga fukuzatsu de, sukoshi oboenikui desu.

This kanji has a complicated stroke order, so it is a little hard to remember.

Rekishi no nengō wa sūji bakari nano de, watashi ni totte wa oboenikui.

Historical dates are nothing but numbers, so they are hard for me to memorize.

Hajimete atta hito no namae wa, ichido de wa oboenikui mono desu.

People's names are naturally hard to remember the first time you meet them.

Kono pasuwādo wa nagasugite oboenikui node, techō ni memo shite okimasu.

This password is too long and hard to remember, so I will write it down in my notebook.

Fukisoku dōshi no henka wa, rūru ga nai node oboenikui.

Conjugations of irregular verbs are hard to memorize because there are no rules.

Kanrensei no nai tango wa, sutōrī ga nai to oboenikui desu.

Words with no connection are hard to remember if there is no story behind them.