ダンダダン [Dan Da Dan] Series by Yukinobu Tatsu

Momo Ayase strikes up an unusual friendship with her school's UFO fanatic, whom she nicknames "Okarun" because he has a name that is not to be said aloud. While Momo believes in spirits, she thinks aliens are nothing but nonsense. Her new friend, meanwhile, thinks the exact opposite. To settle matters, the two set out to prove each other wrong—Momo to a UFO hotspot and Okarun to a haunted tunnel! What unfolds next is a beautiful story of young love…and oddly horny aliens and spirits?

A nerd must fight powerful spirits and aliens all vying for the secret power of his “family jewel,” so who better to fight alongside him than his high school crush and a spirit granny?!Momo Ayase and Okarun are on opposite sides of the paranormal spectrum regarding what they’ll believe in and what they won’t... moreA nerd must fight powerful spirits and aliens all vying for the secret power of his “family jewel,” so who better to fight alongside him than his high school crush and a spirit granny?!Momo Ayase and Okarun are on opposite sides of the paranormal spectrum regarding what they’ll believe in and what they won’t. Their quest to prove each other wrong leads them down a path of secret crushes and paranormal battles they’ll have to participate in to believe!Okarun and Momo search for his precious family jewels, which he lost during his battle with Turbo Granny. Unfortunately, their classmate Aira has already found one, and it’s awakened spiritual powers within her. Around this same time, a strange woman in a red dress appears at their school and attacks them! Who is she, and what’s with her obsession with Aira? less

A nerd must fight powerful spirits and aliens all vying for the secret power of his “family jewel,” so who better to fight alongside him than his high school crush and a spirit granny?!Momo Ayase and Okarun are on opposite sides of the paranormal spectrum regarding what they’ll believe in and what they won’t... moreA nerd must fight powerful spirits and aliens all vying for the secret power of his “family jewel,” so who better to fight alongside him than his high school crush and a spirit granny?!Momo Ayase and Okarun are on opposite sides of the paranormal spectrum regarding what they’ll believe in and what they won’t. Their quest to prove each other wrong leads them down a path of secret crushes and paranormal battles they’ll have to participate in to believe!The Kito clan tosses Okarun and the gang into an alternate-reality version of Jiji’s family home as an offering to the serpent god! Still imprisoned there is a former child sacrifice who goes on to possess the softhearted Jiji, and the two of them become the Evil Eye. When he then attacks Okarun and Momo, Okarun decides to take him on alone and sends Momo back aboveground to get help. There, Momo comes up with an ingenious plan to get rid of the giant serpent god, but can she pull it off on her own in time to save Jiji? less

Okarun and the others emerge victorious in their fight against the serpent god, but one lingering threat remains—the Evil Eye’s possession of Jiji. Even Grandma Seiko’s exorcism is of no use. To complicate matters further, whenever Jiji comes into contact with cold water, the Evil Eye regains control and attacks! Out of options, the group decides their best course of action is to watch over Jiji together until a proper exorcism can be performed—whenever that may be!