He has pains in his side.
Kare wa wakibara ga itai no desu.
he; him; his; boyfriend
topic marker particle; indicates contrast with another option (stated or unstated); adds emphasis
side; flank; illegitimate child; child born by someone other than one's wife
indicates sentence subject (occasionally object); indicates possessive (esp. in literary expressions); but; however; still; and
painful; sore; exceeding
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