Of all the recurring cast members of “Hawaii Five-0,” who returned or were introduced this year, it was the past and present lovers of the main characters who helped create strong drama and tension in several season nine storylines. Recurring characters usually complete a couple of episodes and then we don’t always see them again, but it seems as if three characters have caused a bit more conflict and drama this season. Lost love, past love and new love can cause more drama than even the vilest of villains, and these ladies held true to their characters while adding a strong dimension to the overall storyline of “Hawaii Five-0.”

Two of the recurring cast members — Michelle Borth and Claire van der Boom — portray former or current loves of McGarrett (Alex O’Loughlin) and Danny (Scott Caan), respectively. Brittany Ishibashi also recurred this season as a new love interest for Adam (Ian Anthony Dale). While Five-0 fans are used to seeing Borth and van der Boom since their characters were introduced in the first season, Ishibashi is new to the show.

UNCHANGING LOVE

Borth, who plays Catherine Rollins, was McGarrett’s girlfriend from the start of the series until the fourth season when she leaves him to search for a young boy whose father saved her life in Afghanistan. She returned in the sixth season and before McGarrett can take the plunge and ask her to marry him, she leaves him again to work undercover for the same agency as McGarrett’s mother Doris (Christine Lahti).

Yet Cath seems to return right when someone McGarrett loves is in danger — like she did this season to help McGarrett find Greer (Rochelle Aytes) and find justice for Joe White’s (Terry O’Quinn) death. While she and McGarrett have discussed their relationship and the almost-proposal, they seem to have no ill will toward each other. There still seems to be a bond between them because when they are together he absolutely trusts her and does not question her loyalty. While they are no longer in a romantic relationship, it seems as if Cath will always be a part of his life.

When they are about to part ways in “Hala i ka ala hoʻi ʻole mai” (“Gone on the road from which there is no returning”), McGarrett admits to Cath how Joe brought her into his life by making him promise to ask her out after he almost died in Afghanistan. It was the start of his and Cath’s relationship and both admit they are glad it happened. As Cath says good-bye to McGarrett, her heartfelt, “Until next time” seems to signify more in season 10.

REKINDLED LOVE

Van der Boom plays Rachel Hollander, another recurring character who has been on “Hawaii Five-0” since the first season. Rachel is Danny’s ex-wife, and the mother of his children Grace (Teilor Grubbs) and Charlie (Zach Sulzbach). When we first meet Rachel she is married to Stan Edwards (Mark Deklin) but by the end of the first season, she and Danny have rekindled their relationship and conceived Charlie. Yet Rachel lies to Danny and tells him the baby is actually Stan’s child, and they do not get back together.

Over the years their relationship stays basically friendly and most understand that Danny truly loves Rachel. In the last two seasons, they seem to be getting along better than most divorced couples. Yet it seems as if in this season, especially after Grace’s near-fatal automobile accident in “Ka hauli o ka mea hewa ‘ole, he nalowale koke” (“A bruise inflicted on an innocent person vanishes quickly”, that Danny has forgiven Rachel for lying about Charlie and everything they have fought over for the last nine years. As the two rekindle their love for each other and their children, they definitely seem to have a future together as the show continues.

NEW LOVE

Along with McGarrett and Danny, Adam (Ian Anthony Dale) seems to be tentatively exploring a new relationship with Tamiko (Brittany Ishibashi), his childhood friend, and daughter of yakuza boss Hajime Masuda (Sonny Saito). In “O ke kumu, o ka mana, hoʻopuka ʻia” (“The teacher, the pupil — let it come forth”) Tamiko comes to Five-0 asking him to find her fiance who has skipped out on their wedding. As she is the daughter of his father’s yakuza associate, Adam thinks her father, Masuda, has killed him, especially when Tamiko tells Adam that her fiance works for the FBI. Adam and Five-0 find out what happened to Tamiko’s man, but not before they revisit their childhood friendship and the idea that they were once destined to be together as yakuza heirs.

In the season finale “Hana mao ʻole ka ua o Waianae” (“Endlessly Pours the Rain of Waianae”) Adam seems to be doing more than just comforting his old friend. He shares a friendly breakfast with her after keeping her company while she mourns her dead fiance. Later when he brings her dinner, he does not decline her invitation to stay. It does leave the door open for her return in season 10 — which would be an interesting flip of Adam’s character arc. This time it’s Adam who is on the right side of the law and his potential partner on the yakuza side.

Wendie Burbridge writes the “Five-0 Redux” and “Magnum Reloaded” blogs for staradvertiser.com. Follow her on Twitter and Instagram.