実を言うと、すっかり忘れていたのです。

fruit; nut; seed; (in broth) pieces of meat, vegetable, etc.; content; substance

indicates direct object of action; indicates subject of causative expression; indicates an area traversed; indicates time (period) over which action takes place; indicates point of departure or separation of action; indicates object of desire, like, hate, etc.

to say; to utter; to declare; to name; to call; to go (e.g. "the alarm went ping"); to make a noise

if; when; and; with; particle used for quoting (with speech, thoughts, etc.); quoting particle; promoted pawn; indicates question (sentence end)

all; completely; thoroughly

to forget; to leave carelessly; to be forgetful of; to forget about; to forget (an article)

indicates possessive; nominalizes verbs and adjectives; substitutes for "ga" in subordinate phrases; (at sentence-end, falling tone) indicates a confident conclusion; (at sentence-end) indicates emotional emphasis; (at sentence-end, rising tone) indicates question

be; is